<PAGE>
 
                                                                    EXHIBIT 10.3




                             AMENDMENT NO. SIX TO
                           PLATINUM TECHNOLOGY, INC.
                                 OFFICE LEASE

     THIS AMENDMENT NO. SIX ("Amendment No. Six"), to that certain Oakbrook 
Terrace Corporate Center, Phase III ("Building") Office lease dated May 6, 1992 
("Base Lease"), as previously amended by Amendment No. One to Office lease dated
May 3, 1993, Amendment No. Two to Office Lease dated October 26, 1993, 
Amendment No. Three to Office Lease dated December 22, 1994, Amendment No. Four
to Platinum Technology, Inc. Office Lease dated March 9, 1995 and Amendment No. 
Five to Platinum Technology, Inc. Office Lease dated December 1, 1996, is made 
by and between Oakbrook Terrace Corporate Center III LLC, a Delaware limited 
liability company ("Landlord") and Platinum Technology, Inc., a Delaware 
corporation ("Tenant"), as of the 30th day of April, 1997.


                                   RECITALS:
                                   --------

     A.  Pursuant to Section 28 of the Lease, Tenant has the right to lease 
approximately 7,553 rentable square feet of space (the "Third Option Space") on 
the fourth floor of the Building, effective on the Third Option Space 
Commencement Date, as such term is defined in the Lease and hereinafter, and 
Tenant has advised Landlord that it wishes to lease the Third Option Space as of
the Third Option Space Commencement Date, on the terms and conditions set forth 
herein and in the Lease.

     B.  Pursuant to Section 29 of the Lease, Landlord has advised Tenant of the
availability of the following additional space in the Building:

         (1)  First Offer Space A - 32,132 rentable square feet of space, 
     consisting of (a) 24,400 rentable square feet on the first floor, (b) 3,792
     rentable square feet on the lower level, and (c) 3,940 rentable square feet
     on the lower level; and

         (2)  First Offer Space B - 9,015 rentable square feet on the fifth 
     floor; and

         Tenant has advised Landlord that Tenant wishes to lease First Offer 
     Space A and First Offer Space B on the terms and conditions set forth
     herein.

     NOW, THEREFORE, Landlord and Tenant mutually agree as follows:

     1.  Incorporation of Recitals. The above Recitals are incorporated into the
text of this Amendnent No. Six as though fully set forth herein.


<PAGE>
 
     2.  Lease of Space; Effective Date. Landlord hereby leases to Tenant, and 
Tenant leases from Landlord, the Third Option Space, the First Offer Space A and
the First Offer Space B, effective, with respect to each such space, on the 
following dates:

               (a)  Third Option Space. Tenant has had access to the space 
     beginning March 1, 1997, and shall commence paying Rent as of July 1, 1997
     (the "Third Option Space Commencement Date"), as provided in Section 28 
     of the Lease;

               (b)  First Offer Space A. Tenant has had access to the space 
     beginning April 1, 1997, and shall commence paying Rent as of July 1, 1997
     (the "First Offer Space A Commencement Date") with respect to 12,200
     rentable square feet on the first floor and with respect to all space on
     the lower level, and as of the earlier to occur of (i) September 1, 1997 or
     (ii) the date Tenant takes occupancy of First Offer Space A with respect to
     the remaining 12,200 rentable square feet on the first floor;

               (c)  First Offer Space B. Tenant shall have access to the space 
     as of May 20, 1997, and shall commence paying Rent as of August 20, 1997 
     (the "First Offer Space B Commencement Date").

     3.  Base Rent. Base Rent for the Third Option Space, the First Offer Space 
A and the First Offer Space B shall be paid in installments pursuant to Exhibit 
A attached hereto.

     4.  Percentage Interest. The Tenant's Proportionate Share of the Building 
as set forth in Section 1.K of the Lease is adjusted as follows:

     For the Period                                     Percentage Listed
     --------------                                     -----------------

     July 1, 1997 to August 19, 1997                            .7960199*

     August 20, 1997 to August 31, 1997                         .8324832*

     September 1, 1997 to December 14, 2002                     .8818290


*Increases by .0493457 as of date Tenant commences occupancy of First Offer 
Space A, if prior to September 1, 1997.





                                      -2-
 
<PAGE>
 
     5.   Floors.  Section 1.M. of the Lease is amended as follows:

     July 1, 1997 to August 19 1997:           Tenth Floor (24,500rsf)
                                               Ninth Floor (24,582rsf)
                                               Eighth Floor (24,664rsf)
                                               Seventh Floor (24,746rsf)
                                               Sixth Floor (24,824rsf)
                                               Fifth Floor (1,355rsf)
                                               Fourth Floor (7,553rsf)
                                               Third Floor (25,027rsf)
                                               Second Floor (19,621rsf)
                                               First Floor (12,200rsf)
                                               Lower Level (7,732rsf)

     Total Space Occupied by Tenant                 196,804 rsf*
 
     August 20, 1997 to August 31, 1997:       Tenth Floor (24,500rsf)
                                               Ninth Floor (24,582rsf)
                                               Eighth Floor (24,664rsf)
                                               Seventh Floor (24,746rsf)
                                               Sixth Floor (24,824rsf)
                                               Fifth Floor (10,370rsf)
                                               Fourth Floor (7,553rsf)
                                               Third Floor (25,027rsf)
                                               Second Floor (19,621rsf)
                                               First Floor (12,200rsf)
                                               Lower Level (7,732rsf)


     Total Space Occupied by Tenant                 205,819 rsf*

*This figure increases by 12,200rsf if Tenant commences occupancy of First
Offer Space A prior to September 1, 1997.

     September 1, 1997 to December 14, 2002:   Tenth Floor (24,500rsf)
                                               Ninth Floor (24,582rsf)
                                               Eighth Floor (24,664rsf)
                                               Seventh Floor (24,746rsf)
                                               Sixth Floor (24,824rsf)
                                               Fifth Floor (10,370rsf)
                                               Fourth Floor (7,553rsf)
                                               Third Floor (25,027rsf)
                                               Second Floor (19,621rsf)
                                               First Floor (12,400rsf)
                                               Lower Level (7,732rsf)

     Total Space Occupied by Tenant                 218,019 rsf*

                                     - 3 -
 
<PAGE>
 

     6.  Tenant Improvements. All Improvements associated with the Third Option
Space, the First Offer Space A and the First Offer Space B shall be performed
and constructed by Tenant, at its sole cost and expense, pursuant to Section 38
of the Lease, except that:

          (a) Notwithstanding anything contained in the Lease to the contrary,
     Tenant shall be entitled to a construction allowance for the Third Option
     Space, the First Offer Space A and the First Offer Space B of Eight Hundred
     Seventy-Six Thousand, Six Hundred Dollars ($876,600.00) ($18.00 per
     rentable square foot); and

          (b) To the extent that Tenant does not utilize the full $18.00 per rsf
     construction allowance on any of the Third Option Space, the First Offer
     Space A and the First Offer Space B, respectively, Tenant shall have the
     right to utilize such unused portion of said construction allowance on any
     other of the spaces added to the Lease pursuant to this Amendment No. Six;
     and

          (c) Except for the construction allowance referred to in Section 6(a)
     above, there shall be no other allowance or credit to Tenant with respect
     to the Tenant Improvements to be undertaken by Tenant in the Third Option
     Space, the First Offer Space A and the First Offer Space B.

     7.   Occupancy by Current Tenants.  Tenant acknowledges that Landlord's 
ability to deliver possession of the First Offer Space B on the date provided 
for herein is dependent upon the vacation of such space on or before said date 
by the tenant currently occupying such space.  In the event that such current 
tenant does not vacate the First Offer Space B by the date provided for herein, 
Tenant's obligation hereunder with respect to such space shall remain in full 
force and effect, except that the date upon which (a) Landlord is required to 
deliver possession, (b) the date such space is to be incorporated into the 
Premises and (c) the date upon which Rent is to begin, shall be extended one (1)
day for each day of delay in delivering possession as provided herein to Tenant.

     8.   Credits, Abatements. Notwithstanding anything contained in the Lease,
as amended from time to time, to the contrary, the only credits, abatements or
allowances to which Tenant shall be entitled with respect to the Third Option
Space, the First Offer Space A and the First Offer Space B shall be those set
forth in this Amendment No. Six.

     9.   Brokerage. Landlord and Tenant mutually represent and warrant to each
other that, except for Mesirow Stein Real Estate Inc. ("Tenant's Broker") and
Spaulding and Slye Services Limited Partnership ("Landlord's Broker"), neither
Landlord nor Tenant has dealt with any real estate broker, sales person or
finder in connection with this Lease Amendment No. Six, or showed the Third
Option Space, the First Offer Space A or the First Offer Space B to Tenant.
Landlord and Tenant mutually agree to indemnify, defend and hold harmless the
other party and its officers, directors, partners and employees, from and
against any and all claims, demands, liabilities, actions, damages, costs and
expenses (including attorneys' fees) for brokerage commissions or fees arising
out of a breach of such representation and warranty. Unless otherwise agreed by
the parties, Landlord shall be responsible for the payment of all

                                     - 4 -
 
<PAGE>
 

commissions to Tenant's Broker and Landlord's Broker, based upon the leasing
commission policy of Landlord applicable to the building and in effect as of the
date of this Lease.

     10.  Ratification. Except as provided in this Amendment No. Six, the Lease
shall remain in full force and effect and is hereby ratified and confirmed. To
the extent that any of the covenants, terms and conditions of the Lease conflict
with the covenants, terms and conditions of this Amendment No. Six, the
covenants, terms and conditions of this Amendment No. Six shall govern and
control.

     IN WITNESS WHEREOF, Landlord and Tenant have executed this Amendment No.
Six to Office Lease on the day and in the year first above written.

                                       LANDLORD:
                                       OAKBROOK TERRACE CORPORATE CENTER III LLC
                                    
                                       By:  Spaulding and Slye Services Limited
                                              Partnership, Manager
                                    
                                    
                                    
                                       By:  /s/ Peter A. Bailey   6/30/97
                                            ------------------------------------
                                                Peter A. Bailey, Vice President
                                    
ATTEST:                                TENANT:
                                       PLATINUM TECHNOLOGY, INC.                
                                    
                                       
                                       By:  /s/ R. W. Powell                    
/s/ Larry S. Freedman                       ------------------------------------
------------------------               Its: V.P. Real Estate               
Its: Assistant Secretary                    ------------------------------------


                                     - 5 -
 
<PAGE>
 
                                  EXHIBIT A-1

This worksheet is intended solely as a reference guide. All terms as outlined 
in the accompanying lease amendment #6 and the terms outlined in the Base Lease 
shall govern.

PLATINUM technology, inc.
Monthly Base Rent Summary
Oakbrook Terrace Corporate Center III

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------
Space Name:     Original Premises                  First Expansion Space             First Option Space   
Amendment #     Original Lease                     Original Lease                    1                    
Square Feet:    86,119                             12,373                            11,171               
Description:       24,500    10th Floor            7th Floor                         6th Floor
                   24,582     9th Floor
                   24,664     8th Floor
                   12,373     7th Floor
--------------------------------------------------------------------------------------------------------------------
                             Rent        Monthly                Rent       Monthly                Rent       Monthly 
                Rent/SF   Abatement        Rent    Rent/SF   Abatement       Rent    Rent/SF   Abatement       Rent
--------------------------------------------------------------------------------------------------------------------
<S>             <C>       <C>         <C>          <C>       <C>         <C>         <C>       <C>         <C>
12/15/92          16.00       16.00         0.00
01/01/93          16.00       16.00         0.00
02/01/93          16.00       16.00         0.00
03/01/93          16.00       16.00         0.00
04/01/93          16.00       16.00         0.00                                       11.50       11.50        0.00
05/01/93          16.00       16.00         0.00                                       11.50       11.50        0.00
06/01/93          16.00       16.00         0.00                                       11.50       11.50        0.00
07/01/93          16.00       16.00         0.00                                       11.50       11.50        0.00
08/01/93          16.00       16.00         0.00                                       11.50       11.50        0.00
09/01/93          16.00       16.00         0.00                                       11.50       11.50        0.00
10/01/93          16.00       16.00         0.00                                       11.50       11.50        0.00
11/01/93          16.00       16.00         0.00                                       11.50       11.50        0.00
12/1/93           16.00       16.00         0.00                                       11.50       11.50        0.00
12/15/93          16.40       16.40         0.00                                       11.50       11.50        0.00
--------------------------------------------------------------------------------------------------------------------
01/01/94          16.40       16.40         0.00                                       11.50        4.91    6,137.68
02/01/94          16.40       16.40         0.00                                       11.50        4.91    6,137.68
03/01/94          16.40       16.40         0.00                                       11.50        4.91    6,137.68
04/01/94          16.40       16.40         0.00                                       11.85        4.91    6,458.85
05/01/94          16.40       16.40         0.00                                       11.85        4.91    6,458.85
06/01/94          16.40       16.40         0.00                                       11.85        4.91    6,458.85
07/01/94          16.40       16.40         0.00                                       11.85        4.91    6,458.85
08/01/94          16.40       16.40         0.00                                       11.85        4.91    6,458.85
09/01/94          16.40       16.40         0.00                                       11.85        4.91    6,458.85
10/01/94          16.40       16.40         0.00                                       11.85        4.91    6,458.85
11/01/94          16.40       16.40         0.00                                       11.85        4.91    6,458.85
12/1/94           16.40       16.40         0.00                                       11.85        4.91    2,916.90
12/15/94          16.81       16.81         0.00                                       11.85        4.91    3,541.95
--------------------------------------------------------------------------------------------------------------------
01/01/95          16.81       16.81         0.00                                       11.85        4.91    6,458.85
02/01/95          16.81       16.81         0.00                                       11.85        4.91    6,458.85
03/01/95          16.81       16.81         0.00                                       11.85        4.91    6,458.85
04/01/95          16.81       16.81         0.00                                       12.20        4.91    6,789.65
05/01/95          16.81       16.81         0.00                                       12.20        4.91    6,789.65
06/01/95          16.81       16.81         0.00                                       12.20        4.91    6,789.65
07/01/95          16.81       16.81         0.00                                       12.20        4.91    6,789.65
08/01/95          16.81       16.81         0.00                                       12.20        4.91    6,789.65
09/01/95          16.81       16.81         0.00                                       12.20        4.91    6,789.65
10/01/95          16.81       16.81         0.00                                       12.20        4.91    6,789.65
11/01/95          16.81        7.84    64,340.46                                       12.20        4.91    6,789.65
12/1/95           16.81                54,481.84                                       12.20        4.91    3,066.29
12/15/95          17.23                67,809.45     17.23                9,742.41     12.20        4.91    3,723.36
--------------------------------------------------------------------------------------------------------------------
01/01/96          17.23               123,652.53     17.23               17,765.57     12.20        4.91    6,789.65
02/01/96          17.23               123,652.53     17.23               17,765.57     12.20        4.91    6,789.65
03/01/96          17.23               123,652.53     17.23               17,765.57     12.20        4.91    6,789.65
04/01/96          17.23               123,652.53     17.23               17,765.57     12.57        4.91    7,130.37
05/01/96          17.23               123,652.53     17.23               17,765.57     12.57        4.91    7,130.37
06/01/96          17.23               123,652.53     17.23               17,765.57     12.57        4.91    7,130.37
07/01/96          17.23               123,652.53     17.23               17,765.57     12.57        4.91    7,130.37
08/01/96          17.23               123,652.53     17.23               17,765.57     12.57        4.91    7,130.37
09/01/96          17.23               123,652.53     17.23               17,765.57     12.57        4.91    7,130.37
10/01/96          17.23               123,652.53     17.23               17,765.57     12.57        4.91    7,130.37
11/01/96          17.23               123,652.53     17.23               17,765.57     12.57        4.91    7,130.37
12/1/96           17.23                55,843.08     17.23                8,023.16     12.57        4.91    3,220.17
12/15/96          17.66                69,501.74     17.66                9,985.54     12.57        4.91    3,910.20
--------------------------------------------------------------------------------------------------------------------
01/01/97          17.66               126,738.46     17.66               18,208.93     12.57        4.91    7,130.37
02/01/97          17.66               126,738.46     17.66               18,208.93     12.57        4.91    7,130.37
03/01/97          17.66               126,738.46     17.66               18,208.93     12.57        4.91    7,130.37
04/01/97          17.66               126,738.46     17.66               18,208.93     12.94        4.91    7,481.32
05/01/97          17.66               126,738.46     17.66               18,208.93     12.94        4.91    7,481.32
06/01/97          17.66               126,738.46     17.66               18,208.93     12.94        4.91    7,481.32
07/01/97          17.66               126,738.46     17.66               18,208.93     12.94        4.91    7,481.32
08/01/97          17.66               126,738.46     17.66               18,208.93     12.94        4.91    7,481.32
09/01/97          17.66               126,738.46     17.66               18,208.93     12.94        4.91    7,481.32
10/01/97          17.66               126,738.46     17.66               18,208.93     12.94        4.91    7,481.32
11/01/97          17.66               126,738.46     17.66               18,208.93     12.94        4.91    7,481.32
12/1/97           17.66                57,236.72     17.66                8,223.39     12.94        2.45    3,157.64
12/15/97          18.10                71,233.38     18.10               10,234.33     18.10                9,240.10
--------------------------------------------------------------------------------------------------------------------
01/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
02/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
03/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
04/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
05/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
06/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
07/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
08/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
09/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
10/01/98          18.10               129,896.16     18.10               18,662.61     18.10               16,849.59
</TABLE>

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------
Space Name:     Initial 2nd Expansion Space        3rd Expansion Space               4th Expansion Space  
Amendment #     1                                  1                                 2                    
Square Feet:    6,112                              1,355                             10,652               
Description:    6th Floor                          5th Floor                         2nd Floor
                                       
                                         

--------------------------------------------------------------------------------------------------------------------
                             Rent        Monthly                Rent       Monthly                           Monthly 
                Rent/SF   Abatement        Rent    Rent/SF   Abatement       Rent    Rent/SF   Abatement       Rent
--------------------------------------------------------------------------------------------------------------------
<S>             <C>       <C>         <C>          <C>       <C>         <C>         <C>       <C>         <C>
12/15/92
01/01/93
02/01/93
03/01/93
04/01/93          11.50       11.50         0.00     16.00       16.00       0.00
05/01/93          11.50       11.50         0.00     16.00       16.00       0.00
06/01/93          11.50       11.50         0.00     16.00       16.00       0.00
07/01/93          11.50       11.50         0.00     16.00       16.00       0.00
08/01/93          11.50       11.50         0.00     16.00       16.00       0.00
09/01/93          11.50       11.50         0.00     16.00       16.00       0.00
10/01/93          11.50       11.50         0.00     16.00       16.00       0.00
11/01/93          11.50       11.50         0.00     16.00       16.00       0.00
12/1/93           11.50       11.50         0.00     16.00       16.00       0.00
12/15/93          11.50       11.50         0.00     16.40       16.40       0.00      16.40       16.40        0.00
--------------------------------------------------------------------------------------------------------------------
01/01/94          11.50       11.50         0.00     16.40       16.40       0.00      16.40       16.40        0.00
02/01/94          11.50       11.50         0.00     16.40       16.40       0.00      16.40       16.40        0.00
03/01/94          11.50       11.50         0.00     16.40       16.40       0.00      16.40       16.40        0.00
04/01/94          11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
05/01/94          11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
06/01/94          11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
07/01/94          11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
08/01/94          11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
09/01/94          11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
10/01/94          11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
11/01/94          11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
12/1/94           11.85       11.85         0.00     16.40       16.40       0.00      16.40       16.40        0.00
12/15/94          11.85       11.85         0.00     16.81       16.81       0.00      16.81       16.81        0.00
--------------------------------------------------------------------------------------------------------------------
01/01/95          11.85       11.85         0.00     16.81       16.81       0.00      16.81       16.81        0.00
02/01/95          11.85       11.85         0.00     16.81       16.81       0.00      16.81       16.81        0.00
03/01/95          11.85       11.85         0.00     16.81       16.81       0.00      16.81       16.81        0.00
04/01/95          12.21                 6,218.96     16.81       16.81       0.00      16.81       16.81        0.00
05/01/95          12.21                 6,218.96     16.81       16.81       0.00      16.81       16.81        0.00
06/01/95          12.21                 6,218.96     16.81       16.81       0.00      16.81       16.81        0.00
07/01/95          12.21                 6,218.96     16.81       16.81       0.00      16.81       16.81        0.00
08/01/95          12.21                 6,218.96     16.81       16.81       0.00      16.81               14,921.68
09/01/95          12.21                 6,218.96     16.81       16.81       0.00      16.81               14,921.68
10/01/95          12.21                 6,218.96     16.81       16.81       0.00      16.81               14,921.68
11/01/95          12.21                 6,218.96     16.81       16.81       0.00      16.81               14,921.68
12/1/95           12.21                 2,808.56     16.81       16.81       0.00      16.81                6,738.82
12/15/95          12.21                 3,410.40     17.23       17.23       0.00      17.23                8,387.30 
--------------------------------------------------------------------------------------------------------------------
01/01/96          12.21                 6,218.96     17.23       17.23       0.00      17.23               15,294.50
02/01/96          12.21                 6,218.96     17.23       17.23       0.00      17.23               15,294.50
03/01/96          12.21                 6,218.96     17.23       17.23       0.00      17.23               15,294.50
04/01/96          12.58                 6,407.41     17.23               1,945.55      17.23               15,294.50
05/01/96          12.58                 6,407.41     17.23               1,945.55      17.23               15,294.50
06/01/96          12.58                 6,407.41     17.23               1,945.55      17.23               15,294.50
07/01/96          12.58                 6,407.41     17.23               1,945.55      17.23               15,294.50
08/01/96          15.13                 7,706.21     17.23               1,945.55      17.23               15,294.50
09/01/96          17.23                 8,775.81     17.23               1,945.55      17.23               15,294.50
10/01/96          17.23                 8,775.81     17.23               1,945.55      17.23               15,294.50
11/01/96          17.23                 8,775.81     17.23               1,945.55      17.23               15,294.50
12/1/96           17.23                 3,963.27     17.23                 878.64      17.23                6,907.19
12/15/96          17.66                 4,932.65     17.66               1,093.54      17.66                8,596.62
--------------------------------------------------------------------------------------------------------------------
01/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
02/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
03/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
04/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
05/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
06/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
07/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
08/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
09/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
10/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
11/01/97          17.66                 8,994.83     17.66               1,994.11      17.66               15,676.19
12/1/97           17.66                 4,062.18     17.66                 900.57      17.66                7,079.57
12/15/97          18.10                 5,055.54     18.10               1,120.79      18.10                8,810.81
--------------------------------------------------------------------------------------------------------------------
01/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
02/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
03/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
04/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
05/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
06/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
07/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
08/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
09/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
10/01/98          18.10                 9,218.93     18.10               2,043.79      18.10               16,066.77
</TABLE>

<TABLE>
<CAPTION>
--------------------------------------------------------------------------------------------------------------------
Space Name:     Balance 2nd Expansion Space        5th Expansion Space               6th Expansion Space  
Amendment #     3 (5)                              3                                 4                    
Square Feet:    7,541                              6,919                             27,077               
Description:    6th Floor                          2nd Floor                            25,027 3rd Floor
                                                                                         2,050 2nd Floor
                                         

--------------------------------------------------------------------------------------------------------------------
                                         Monthly                           Monthly                Rent       Monthly 
                Rent/SF   Abatement        Rent    Rent/SF   Abatement       Rent    Rent/SF   Abatement       Rent
--------------------------------------------------------------------------------------------------------------------
<S>             <C>       <C>         <C>          <C>       <C>         <C>         <C>       <C>         <C>
12/15/92
01/01/93
02/01/93
03/01/93
04/01/93
05/01/93
06/01/93
07/01/93
08/01/93
09/01/93
10/01/93
11/01/93
12/1/93 
12/15/93
--------------------------------------------------------------------------------------------------------------------
01/01/94
02/01/94
03/01/94
04/01/94
05/01/94
06/01/94
07/01/94
08/01/94
09/01/94
10/01/94
11/01/94
12/1/94           16.40       16.40         0.00
12/15/94          16.81       16.81         0.00
--------------------------------------------------------------------------------------------------------------------
01/01/95          16.81       16.81         0.00
02/01/95          16.81       16.81         0.00
03/01/95          14.04                 8,822.97
04/01/95          14.04                 8,822.97
05/01/95          14.04                 8,822.97
06/01/95          14.04                 8,822.97     16.81       16.81       0.00      16.81       16.81        0.00
07/01/95          14.04                 8,822.97     16.81       16.81       0.00      16.81       16.81        0.00
08/01/95          14.04                 8,822.97     16.81       16.81       0.00      16.81       16.81        0.00
09/01/95          14.04                 8,822.97     13.39               7,720.45      16.81               37,930.36
10/01/95          14.04                 8,822.97     13.39               7,720.45      16.81               37,930.36
11/01/95          14.04                 8,822.97     13.39               7,720.45      16.81               37,930.36
12/1/95           14.04                 3,984.57     13.39               3,486.66      16.81               17,129.84
12/15/95          14.46                 4,983.14     13.81               4,366.60      17.23               21,320.23
--------------------------------------------------------------------------------------------------------------------
01/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
02/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
03/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
04/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
05/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
06/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
07/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
08/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
09/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
10/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
11/01/96          14.46                 9,086.91     13.81               7,962.62      17.23               38,878.06
12/1/96           14.46                 4,103.76     13.81               3,596.02      17.23               17,557.83
12/15/96          14.89                 5,131.33     14.24               4,502.56      17.66               21,852.30
--------------------------------------------------------------------------------------------------------------------
01/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
02/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
03/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
04/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
05/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
06/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
07/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
08/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
09/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
10/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
11/01/97          14.89                 9,357.12     14.24               8,210.55      17.66               39,848.32
12/1/97           14.89                 4,225.80     14.24               3,707.99      17.66               17,996.01
12/15/97          15.33                 5,282.96     14.68               4,641.68      18.10               22,396.76
--------------------------------------------------------------------------------------------------------------------
01/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14 
02/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14  
03/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14 
04/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14  
05/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14  
06/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14  
07/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14  
08/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14  
09/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14  
10/01/98          15.33                 9,633.63     14.68               8,464.24      18.10               40,841.14  
</TABLE>


<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------------------------
Space Name:     Third Option Space                 First Offer Space A               First Offer Space B               Totals
Amendment #     6                                  6                                 6                                
Square Feet:    7,553                              32,132                            9,015                             218,019
Description:    4th Floor                             24,400 1st Floor               5th  Floor
                                                       3,792 LL Fitness Ctr.         
                                                       3,940 LL Conference Ctr. 

---------------------------------------------------------------------------------------------------------------------------------
                             Rent        Monthly                Rent       Monthly                Rent       Monthly   Total From
                Rent/SF   Abatement        Rent    Rent/SF   Abatement       Rent    Rent/SF   Abatement       Rent        Detail
---------------------------------------------------------------------------------------------------------------------------------
<S>             <C>       <C>         <C>          <C>       <C>         <C>         <C>       <C>         <C>         <C> 
12/15/92                                                                                                                     0.00   
01/01/93                                                                                                                     0.00   
02/01/93                                                                                                                     0.00   
03/01/93                                                                                                                     0.00   
04/01/93                                                                                                                     0.00   
05/01/93                                                                                                                     0.00   
06/01/93                                                                                                                     0.00   
07/01/93                                                                                                                     0.00   
08/01/93                                                                                                                     0.00   
09/01/93                                                                                                                     0.00   
10/01/93                                                                                                                     0.00   
11/01/93                                                                                                                     0.00   
12/1/93                                                                                                                      0.00   
12/15/93
---------------------------------------------------------------------------------------------------------------------------------
01/01/94                                                                                                                 6,137.68
02/01/94                                                                                                                 6,137.68
03/01/94                                                                                                                 6,137.68
04/01/94                                                                                                                 6,458.85
05/01/94                                                                                                                 6,458.85
06/01/94                                                                                                                 6,458.85
07/01/94                                                                                                                 6,458.85
08/01/94                                                                                                                 6,458.85
09/01/94                                                                                                                 6,458.85
10/01/94                                                                                                                 6,458.85
11/01/94                                                                                                                 6,458.85
12/1/94                                                                                                                  6,458.85
12/15/94
---------------------------------------------------------------------------------------------------------------------------------
01/01/95                                                                                                                 6,458.85
02/01/95                                                                                                                 6,458.85
03/01/95                                                                                                                15,281.82
04/01/95                                                                                                                21,831.58
05/01/95                                                                                                                21,831.58
06/01/95                                                                                                                21,831.58
07/01/95                                                                                                                21,831.58
08/01/95                                                                                                                36,753.26
09/01/95                                                                                                                82,404.07
10/01/95                                                                                                                82,404.07
11/01/95                                                                                                               146,744.53
12/1/95                                                                                                                215,439.47
12/15/95
---------------------------------------------------------------------------------------------------------------------------------
01/01/96                                                                                                               225,648.78
02/01/96                                                                                                               225,648.78
03/01/96                                                                                                               225,648.78
04/01/96                                                                                                               228,123.51
05/01/96                                                                                                               228,123.51
06/01/96                                                                                                               228,123.51
07/01/96                                                                                                               228,123.51
08/01/96                                                                                                               229,422.31
09/01/96                                                                                                               230,491.91
10/01/96                                                                                                               230,491.91
11/01/96                                                                                                               230,491.91
12/1/96                                                                                                                233,599.60
12/15/96
---------------------------------------------------------------------------------------------------------------------------------
01/01/97                                                                                                               236,158.88
02/01/97                                                                                                               236,158.88
03/01/97                                                                                                               236,158.88
04/01/97                                                                                                               236,509.83
05/01/97                                                                                                               236,509.83
06/01/97                                                                                                               236,509.83
07/01/97          17.66                11,115.50     17.66              29,333.26                                      276,958.59
08/01/97          17.66                11,115.50     17.66              29,333.26      17.66                5,135.64   282,094.23
09/01/97          17.66                11,115.50     17.66              47,287.59      17.66               13,267.08   308,180.00
10/01/97          17.66                11,115.50     17.66              47,287.59      17.66               13,267.08   308,180.00
11/01/97          17.66                11,115.50     17.66              47,287.59      17.66               13,267.08   308,180.00
12/1/97           17.66                 5,019.90     17.66              21,355.69      17.66                5,991.58   317,255.61
12/15/97          18.10                 6,247.47     18.10              26,578.00      18.10                7,456.76   
---------------------------------------------------------------------------------------------------------------------------------
01/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
02/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
03/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
04/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
05/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
06/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
07/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
08/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
09/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
10/01/98          18.10                11,392.44     18.10              48,465.77      18.10               13,597.63   325,132.70
</TABLE>

 
<PAGE>
 
                                  EXHIBIT A-1

PLATINUM technology, inc.
Monthly Base Rent Summary
Oakbrook Terrace Corporate Center III

This worksheet is intended solely as a reference guide. All terms as outlined in
the accompanying lease amendment #6 and the terms outlined in the Base Lease
shall govern.

<TABLE>
<CAPTION>
------------------------------------------------------------------------------------------------------------------------------------
<S>              <C>                         <C>                        <C>                          <C>
Space Name:      Original Premises           First Expansion Space      First Option Space           Initial 2nd Expansion Space
Amendment #      Original Lease              Original Lease             1                            1
Square Feet:     86,119                      12,373                     11,171                       6,112
Description:          24,500  10th Floor     7th Floor                  6th Floor                    6th Floor
                      24,582   9th Floor
                      24,664   8th Floor
                      12,373   7th Floor
11/01/98               18.10   129,896.16        18.10    18,662.61         18.10   16,849.59                18.10      9,218.93
12/01/98               18.10    58,662.78        18.10     8,428.27         18.10    7,609.49                18.10      4,163.39
12/15/98               18.56    73,043.73        18.56    10,494.43         18.56    9,474.93                18.56      5,184.03
------------------------------------------------------------------------------------------------------------------------------------
01/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
02/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
03/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
04/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
05/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
06/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
07/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
08/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
09/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
10/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
11/01/99               18.56   133,197.39        18.56    19,136.91         18.56   17,277.81                18.56      9,453.23
12/01/99               18.56    60,153.66        18.56     8,642.47         18.56    7,802.88                18.56      4,269.20
12/15/99               19.02    74,854.08        19.02    10,754.53         19.02    9,709.76                19.02      5,312.51
------------------------------------------------------------------------------------------------------------------------------------
01/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
02/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
03/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
04/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
05/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
06/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
07/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
08/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
09/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
10/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
11/01/00               19.02   136,498.62        19.02    19,611.21         19.02   17,706.04                19.02      9,687.52
12/01/00               19.02    61,644.54        19.02     8,856.67         19.02    7,996.27                19.02      4,375.01
12/15/00               19.50    76,743.14        19.50    11,025.94         19.50    9,954.80                19.50      5,446.58
------------------------------------------------------------------------------------------------------------------------------------
01/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
02/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
03/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
04/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
05/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
06/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
07/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
08/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
09/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
10/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
11/01/01               19.50   139,943.38        19.50    20,106.13         19.50   18,152.88                19.50      9,932.00
12/01/01               19.50    63,200.23        19.50     9,080.19         19.50    8,198.07                19.50      4,485.42
12/15/01               19.99    78,671.56        19.99    11,303.00         19.99   10,204.95                19.99      5,583.44
------------------------------------------------------------------------------------------------------------------------------------
01/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
02/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
02/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
04/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
05/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
06/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
07/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
08/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
09/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
10/01/92               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
11/01/02               19.99   143,459.90        19.99    20,611.36         19.99   18,609.02                19.99     10,181.57
12/01/02               19.99    64,788.34        19.99     9,308.35         19.99    8,404.08                19.99      4,598.13
------------------------------------------------------------------------------------------------------------------------------------
<CAPTION> 
Space Name:      3rd Expansion Space               4th Expansion Space             Balance 2nd Expansion Space
Amendment #      1                                 2                               3 (5)
Square Feet:     1,355                             10,652                          7,541
Description:     5th Floor                         2nd Floor                       6th Floor

<S>              <C>                               <C>                             <C>
11/01/98               18.10     2,043.79            18.10   16,066.77                15.33   9,633.63
12/01/98               18.10       923.00            18.10    7,255.96                15.33   4,350.67
12/15/98               18.56     1,149.27            18.56    9,034.73                15.79   5,441.48
------------------------------------------------------------------------------------------------------------------------------------
01/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
02/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
03/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
04/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
05/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
06/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
07/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
08/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
09/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
10/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
11/01/99               18.56     2,095.73            18.56   16,475.09                15.79   9,922.70
12/01/99               18.56       946.46            18.56    7,440.36                15.79   4,481.22
12/15/99               19.02     1,777.76            19.02    9,258.65                16.25   5,600.00
------------------------------------------------------------------------------------------------------------------------------------
01/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
02/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
03/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
04/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
05/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
06/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
07/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
08/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
09/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
10/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
11/01/00               19.02     2,147.68            19.02   16,883.42                16.25  10,211.77
12/01/00               19.02       969.92            19.02    7,624.77                16.25   4,611.77
12/15/00               19.50     1,207.48            19.50    9,492.31                16.73   5,765.42
------------------------------------------------------------------------------------------------------------------------------------
01/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
02/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
03/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
04/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
05/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
06/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
07/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
08/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
09/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
10/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
11/01/01               19.50     2,201.88            19.50   17,309.50                16.73  10,513.41
12/01/01               19.50       994.40            19.50    7,817.19                16.73   4,747.99
12/15/01               19.99     1,237.82            19.99    9,730.83                17.22   5,934.28
------------------------------------------------------------------------------------------------------------------------------------
01/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
02/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
02/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
04/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
05/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
06/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
07/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
08/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
09/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
10/01/92               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
11/01/02               19.99     2,257.20            19.99   17,744.46                17.22  10,821.34
12/01/02               19.99     1,019.38            19.99    8,013.63                17.22   4,887.05
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>
<TABLE> 
<CAPTION> 
------------------------------------------------------------------------------------------------------------------------------------
Space Name:      5th Expansion Space               6th Expansion Space             Third Option Space
Amendment #      3                                 4                               3 (5)
Square Feet:     6,919                             27,077                          7,553
Description:     2nd Floor                            25,027 3rd Floor             4th Floor
                                                       2,050 2nd Floor

<S>              <C>                               <C>                             <C>
11/01/98               14.68    8,464.24            18.10    40,841.14               18.10     11.392.44
12/01/98               14.68    3,822.56            18.10    18,444.39               18.10      5,144.97
12/15/98               15.14    4,787.13            18.56    22,965.95               18.56      6,406.24
------------------------------------------------------------------------------------------------------------------------------------
01/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
02/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
03/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
04/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
05/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
06/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
07/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
08/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
09/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
10/01/99               15.14    8,729.47            18.56    41,879.09               18.56     11.681.97
11/01/99               15.14    8,729.47            18.56    41,879.09               18.56      5,275.73
12/01/99               15.14    3,942.34            18.56    18,913.14               19.02      6,565.02
12/15/99               15.60    4,932.58            19.02    23,535.15
------------------------------------------------------------------------------------------------------------------------------------
01/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
02/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
03/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
04/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
05/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
06/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
07/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
08/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
09/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
10/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
11/01/00               15.60    8,994.70            19.02    42,917.05               19.02     11,971.51
12/01/00               15.60    4,062.12            19.02    19,381.89               19.02      5,406,49
12/15/00               16.08    5,084.35            19.50    24,129.10               19.50      6,730.70
------------------------------------------------------------------------------------------------------------------------------------
01/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
02/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
03/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
04/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
05/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
06/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
07/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
08/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
09/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
10/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
11/01/01               16.08    9,271.46            19.50    44,000.13               19.50     12,273.63
12/01/01               16.08    4,187.11            19.50    19,871.02               19.50      5,542.93
12/15/01               16.57    5,239.28            19.99    24,735.42               19.99      6,899.83
------------------------------------------------------------------------------------------------------------------------------------
01/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
02/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
02/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
04/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
05/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
06/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
07/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
08/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
09/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
10/01/92               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
11/01/02               16.57    9,553.99            19.99    45,105.77               19.99     12,582.04
12/01/02               16.57    4,314.70            19.99    20,370.35               19.99      5,682.21
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>
<TABLE> 
<CAPTION> 
------------------------------------------------------------------------------------------------------------------------------------
Space Name:          First Offer Space A            First Offer Space B        Totals
Amendment #          6                              6
Square Feet:         32,132                         9,015                     218.019
Description:            24,400  1st Floor           5th Floor
                         3,792  LL Fitness Ctr.
                         3,940  LL Conference Ctr.

<S>                     <C>                          <C>                     <C>  
11/01/98                 18.10   48,465.77              18.10   13,597.63    325,132.70
12/01/98                 18.10   21,887.77              18.10    6,140.86    329,715.78
12/15/98                 18.56   27,253.46              18.56    7,646.27
------------------------------------------------------------------------------------------------------------------------------------
01/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
02/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
03/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
04/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
05/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
06/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
07/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
08/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
09/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
10/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
11/01/99                 18.56   49.697.49              18.56   13,943.20    333,490.09
12/01/99                 18.56   22,444.03              18.56    6,296.93    338,073.18
12/15/99                 19.02   27,928.93              19.02    7,835.78
------------------------------------------------------------------------------------------------------------------------------------
01/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
02/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
03/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
04/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
05/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
06/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
07/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
08/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
09/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
10/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
11/01/00                 19.02   50,929.22              19.02   14,288.78    341,847.49
12/01/00                 19.02   23,000.29              19.02    6,453.00    346,629.84
12/15/00                 19.50   28,633.76              19.50    8,033.53
------------------------------------------------------------------------------------------------------------------------------------
01/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
02/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
03/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
04/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
05/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
06/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
07/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
08/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
09/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
10/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
11/01/01                 19.50   52.214.50              19.50   14,649.38    350,568.25
12/01/01                 19.50   23,580.74              19.50    6,615 85    355,450.23
12/15/01                 19.99   29,353.27              19.99    8,235.40
------------------------------------------------------------------------------------------------------------------------------------
01/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
02/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
02/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
04/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
05/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
06/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
07/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
08/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
09/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
10/01/92                 19.99   53,526.56              19.99   15,017.49    359,470.69
11/01/02                 19.99   53,526.56              19.99   15,017.49    359,470.69
12/01/02                 19.99   24,173.28              19.99    6,782.09    162,341.60
------------------------------------------------------------------------------------------------------------------------------------
</TABLE>