Document:

<PAGE>
                                                                   EXHIBIT 10.26

                           LISTING AGREEMENT AMENDMENT

Approved by Legal Counsel 1/99

         THIS LISTING AGREEMENT AMENDMENT, made on October 20, 2001, between EBS
Building, L.L.C. (hereinafter called "OWNER"), and Colliers Turley Martin Tucker
Company, (hereinafter called "BROKER").

                                   WITNESSETH

         WHEREAS OWNER and BROKER entered into an Exclusive Listing Agreement
dated April 21, 2000 (hereinafter called ("AGREEMENT") for certain real property
located at 501 North Broadway for a term commencing April 21, 2000 and ending
October 31, 2001.

         WHEREAS OWNER and BROKER desire to amend said AGREEMENT,

         NOW, THEREFORE, IT IS HEREBY AGREED AS FOLLOWS:

         That said AGREEMENT is amended effective October 31, 2001 as follows:

                  SAID AGREEMENT SHALL BE EXTENDED TO EXPIRE/END ON October 31,
                  2002, subject in all respects to the early termination rights
                  afforded Owner and Broker in Section 2 of the Agreement.

                  THE LISTING AGREEMENT IS FURTHER AMENDED AS FOLLOWS:
                  The reference in the first recital of the Agreement to "500
                  North Broadway" is hereby amended to be "501 North Broadway".

         That this LISTING AGREEMENT AMENDMENT shall be subject to all of the
same terms and conditions contained in the Agreement except as hereinabove
stated to the contrary.

         IN WITNESS WHEREOF, OWNER and BROKER have caused this Listing Agreement
Amendment to be executed as of the day and year first above written.

Owner: EBS Building, L.L.C.                 Broker: Colliers Turley Martin
       by PricewaterhouseCoopers, LLP,              Tucker Company
       its manager

By: /s/ Keith F. Cooper                     By: /s/ Scott Bazoian
   -----------------------------------         ---------------------------------

Title: Partner                              Title: Managing Principal
      --------------------------------            ------------------------------

Date: 10/20/01                              Date: 10/16/01
     ---------------------------------           -------------------------------<PAGE>
                                                                   EXHIBIT 10.27

                         [NORTHMARQ CAPITAL LETTERHEAD]

November 5, 2001                                            Delivered Personally

Mr. Lauren D. Hogan
Senior Vice President
Heitman Real Estate Services Group
180 North LaSalle Street, Suite 3400
Chicago, IL 60601

RE: ONE FINANCIAL PLAZA - ST. LOUIS, MISSOURI

Dear Lauren:

This letter (the "Agreement") shall authorize NorthMarq Capital, Inc.
("NorthMarq"), with the exclusive right to procure commitments for financing for
the referenced 12-story, 436,106 square foot office building (the "Property") on
behalf of Heitman Real Estate Services Group and EBS Building L.L.C. ("EBS")
with the following capital sources ("Sources"):

<Table>
<S>                             <C>                          <C>                          <C>
AEGON                           Nationwide                   CDC Mortgage                 Morgan Stanley
Allstate                        Northwestern Mutual          CIBC                         PNC
CIGNA                           NYSTERS                      Column                       Wells Fargo
David L. Babson                 PPM                          Deutsche Bank                Allegiance
GE Financial Assurance          Principal                    First Union                  Capital Trust
ING                             Prudential                   GE Capital                   Capri
John Hancock                    SunAmerica                   Greenwich                    Fleet Bank
Lend Lease                      TIAA                         JP Morgan                    iStar
MetLife                         NY Life                      Lehman                       ORIX
MONY                            Bear, Stearns                Merrill Lynch                TransAmerica
</Table>

NorthMarq is hereby retained by EBS to negotiate and obtain a commitment to
finance the Property from the Sources for which NorthMarq will be compensated as
provided below. Said financing transaction may include a first mortgage,
mezzanine loan or any other debt transaction acceptable to EBS. Should EBS
execute a financing commitment for the Property from one of the Sources, EBS
hereby agrees to pay NorthMarq a net fee equal to three-quarters of one percent
(3/4%) of the total gross loan amount committed by such Source and accepted by
EBS. All fees to NorthMarq shall be paid in full in cash upon the initial
funding of such loan.

The term of this assignment is from the date of acceptance of this Agreement
through February 28, 2002. However, should discussions be in progress with a
Source at the expiration of its term NorthMarq shall so designate in writing and
this Agreement shall be extended automatically for additional thirty (30) day
terms as necessary to conclude such negotiations.

NorthMarq agrees to keep all information pertaining to EBS confidential except
to the extent disclosure is required in connection with NorthMarq's performance
of its obligations hereunder.

<PAGE>

Mr. Lauren D. Hogan
November 5, 2001
Page 2

NorthMarq's obligations under this letter may not be assigned to any other
person or entity without EBS' prior written consent in each instance.

NorthMarq acknowledges that it is acting as an independent contractor under this
letter. Nothing contained in this letter or in the relationship it establishes
shall be deemed to create a partnership, joint venture, or other similar
relationship between NorthMarq or EBS. NorthMarq's authority is limited to
performing the services described in this letter, and under no circumstances
shall NorthMarq have the authority, or represent itself as having the authority,
to commit or otherwise obligate EBS or to negotiate or execute any contracts for
or on behalf of EBS. All terms and conditions of any contract are subject to
prior written approval by EBS, in EBS' sole and absolute discretion.

NorthMarq agrees to indemnify EBS and hold EBS harmless from and against any and
all loss, cost, damage, injury and expense (including reasonable attorneys'
fees) arising out of or relating to any claims or assertions against EBS by any
person, firm or entity for (a) reliance on services, information or materials
supplied by NorthMarq not otherwise received from EBS or its advisors in
connection with NorthMarq's activities hereunder, and (b) any claims against EBS
alleging any misrepresentations made by NorthMarq. In the event any dispute,
litigation or proceeding shall arise between NorthMarq and EBS, the prevailing
party shall be entitled to full reimbursement of all reasonable court costs,
expenses and attorneys' fees from the non-prevailing party. This paragraph shall
survive the expiration or termination of this letter.

NorthMarq is hereby authorized to advertise and promote a financing transaction
for the Property at NorthMarq's sole cost and expense, and shall (i) afford EBS
the full benefit of the judgment, experience and advise of the members of
NorthMarq's organization in respect to the policy to be pursued in financing the
Property; (ii) undertake all other reasonable efforts to secure suitable
financing for the Property; (iii) provide in writing at least every four weeks
during the term of this letter a progress report summarizing the activities
undertaken by NorthMarq in connection with the Property during such period and
NorthMarq's recommendations to expedite a financing; (iv) promptly submit all
financing commitments to EBS; and (v) use its best skill, care and judgment so
as to maintain the highest level of professionalism at all times in all dealings
in connection with representing EBS as provided for herein; provided, however,
that EBS shall maintain all authority with respect to negotiation and acceptance
of any financing and all advertising and press release material to be
distributed or published by NorthMarq shall be subject to the prior written
approval of EBS.

Please indicate the understanding and acceptance of EBS as to the terms and
conditions of this Agreement by executing and returning this letter to us. Thank
you.

Sincerely,
NORTHMARQ CAPITAL, INC.

/s/ DEAN F. DORNBOS                          AGREED TO AND ACCEPTED BY:
                                             EBS BUILDING L.L.C.
Dean F. Dornbos
Managing Director
                                             By:  /s/ KEITH F. COOPER
                                                --------------------------------
                                                 PricewaterhouseCoopers LLP
                                                 As Manager<PAGE>
                                                                   EXHIBIT 10.28

                           EXCLUSIVE LISTING AGREEMENT

                  THIS EXCLUSIVE LISTING AGREEMENT ("Agreement") is made as of
the 10th day of December, 2001, by and between EBS BUILDING, L.L.C., a Delaware
limited liability company, c/o PricewaterhouseCoopers LLP, 800 Market Street,
Suite 1800, St. Louis, Missouri 63101 ("Owner") and COLLIERS TURLEY MARTIN
TUCKER, INC. , a Missouri corporation, 7701 Forsyth, Suite 500, Clayton,
Missouri 63105 ("Broker").

                                   WITNESSETH:

                  WHEREAS, Owner owns the building presently known as One
Financial Plaza, with an address of 501 North Broadway, in St. Louis, Missouri,
appurtenant related parking facilities (partly owned in fee, partly by
leasehold) and appurtenant common areas (hereinafter, together with the real
estate on which the same are situated, collectively referred to as the
"Property"); and

                  WHEREAS, Owner desires to engage Broker as Owner's agent to
sell the Property and Broker desires to accept such engagement, upon and subject
to the terms and conditions set forth herein.

                  NOW, THEREFORE, for and in consideration of the mutual
agreements set forth in this Agreement, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
Owner and Broker hereby agree as follows:

1.       EXCLUSIVE RIGHT TO LIST

         Owner hereby grants to Broker the exclusive right to sell the Property
         for the term of this Agreement. Notwithstanding anything to the
         contrary herein or elsewhere, all terms and conditions of an agreement
         with any prospective purchaser shall be subject to Owner's sole and
         absolute discretion. Owner has the absolute right in all events to
         approve or to disapprove any and all proposals regarding pricing,
         marketing and terms of sale of the Property. Broker shall have no
         authority to extend any offer or make any agreement on behalf of or
         binding on Owner, and Broker shall have no authority to accept security
         or other deposits in connection with any offer to purchase the
         Property; accordingly, an agreement to sell the Property shall become
         effective only when (a) signed by an authorized signatory on behalf of
         Owner and the prospective purchaser and (b) delivered by Owner to such
         prospective purchaser.

2.       TERM

         The term of this Agreement shall end, and this Agreement shall
         terminate and be of no further force and effect, on August 31, 2002;
         provided, however, that (a) Owner and Broker shall each have the right
         to terminate this Agreement and end the term without cause at any time
         by providing thirty (30) day's prior written notice to the other party,
         (b) Owner shall have the further right to terminate this Agreement and
         end the term without cause immediately upon the termination of Owner as
         a limited liability company or termination of

<PAGE>

         the operating agreement dated as of September 26, 1997, under which
         Owner is constituted, (c) Owner shall have the further right to
         terminate this Agreement and end the term without cause immediately
         upon the sale, merger or consolidation of Owner and (d) Owner and
         Broker shall each have the right to terminate this Agreement and end
         the term for cause immediately upon giving written notice of such cause
         and such termination to the other party.

3.       DUTIES OF BROKER

         Broker accepts the relationship of trust and confidence established
         between Broker and Owner under this Agreement. Broker agrees to take
         all actions reasonably required or helpful in selling the Property as
         promptly as possible, including promoting and marketing the Property
         for sale, using its diligent and best efforts, skill, judgment, and
         abilities to show the Property, offering the Property for sale,
         procuring prospective purchasers for Property, cooperating with outside
         brokers representing such prospective purchasers, obtaining financial
         and reference information on prospective purchasers, promptly
         submitting all offers to purchase the Property to Owner, and other
         actions as may be directed by Owner from time to time. Inquiries
         regarding the Property shall be referred to Broker, and related
         negotiations shall be handled by or under direction of Broker, subject
         to the approval and review of Owner and subject to the participation of
         legal counsel selected and retained by Owner to assist as necessary in
         preparation and negotiation of the sale contract and to institute and
         defend any and all legal proceedings associated with the sale of the
         Property; provided that no such legal proceedings or compromises or
         settlements of such legal proceedings shall be undertaken or defended
         without, in each instance, the prior written approval of Owner. Without
         limiting the generality of the foregoing, Broker specifically agrees to
         provide monthly activity reports to Owner on or before the 20th day of
         each calendar month, detailing the activities undertaken by Broker in
         connection with the sale of the Property, including, but not limited
         to, any outstanding offers, prospects shown the Property, active
         prospects, and other marketing activities. Notwithstanding anything to
         the contrary herein or elsewhere, Broker shall perform its duties under
         this Agreement at its own expense and shall be entitled to no
         reimbursement of costs other than as expressly provided in Sections 4,
         5 and 6 of this Agreement.

4.       COMMISSION ON SALE

         Upon the sale of the Property pursuant to a written sale contract
         executed during the term of this Agreement by a purchaser procured by
         Broker, Owner agrees to pay to Broker a commission in accordance with
         Exhibit A attached hereto and incorporated herein by reference. The
         commission shall be earned, due and payable in full at the time of the
         transfer of title to the Property. If a cooperating broker has
         participated in procuring a sale, Broker shall be responsible for
         paying any and all commissions to the cooperating broker after Broker
         is paid by Owner, and Broker shall indemnify and hold Owner harmless
         from and against the claims of any cooperating broker with claims
         arising from a cooperating broker relationship initiated by or through
         Broker including, but not limited to, attorneys' fees and expenses in
         connection with Owner's defense against such claims.

                                       2
<PAGE>

         Owner reserves the right to adjust the asking price, modify the
         marketing plan or withdraw the Property from the market, without being
         liable for any commission hereunder, at its discretion throughout the
         term of this Agreement. Broker shall not be entitled to any commission
         with respect to offers to purchase which, when submitted to Owner for
         approval pursuant to this Agreement, shall, for any reason, be rejected
         by Owner. Broker's commission shall be deemed earned and payable when,
         and only if, title passes to a purchaser of the Property. Owner shall
         not have any obligation to sue any prospective purchaser who defaults
         under the terms of a binding contract of sale for damages or specific
         performance. In the event a prospective purchaser defaults and Owner
         becomes entitled to such prospective purchaser's earnest deposit, then
         such earnest deposit shall be forfeited to Owner as liquidated damages,
         and Broker shall not be entitled to any part thereof. No commission
         will be deemed earned and payable in the event the Property or any
         portion thereof is (i) taken by a municipality or other authority in a
         condemnation or similar proceeding or by deed in lieu thereof or (ii)
         acquired by a lender under a foreclosure proceeding or other similar
         process.

5.       POST-TERMINATION COMMISSIONS

         Within ten (10) days following the termination of this Agreement,
         Broker may submit to Owner a written list of any person or entity
         proposed by Broker during the term of this Agreement as a prospective
         purchaser of the Property with whom Broker had substantial
         negotiations, as defined below, during the term of this Agreement. The
         term "substantial negotiations" shall mean that (a) Broker provided
         marketing materials regarding the Property and (b) either Broker
         brought the prospective purchasers to the Property, the prospective
         purchaser had negotiations with Owner or Broker received a signed
         letter of intent. Broker's list shall include the names and addresses
         of such prospective purchasers and supporting documentation of such
         negotiations. Broker shall have no claim of commission (and hereby
         waives any claim of commission) with respect to any person or entity
         procured or claimed to have been procured by Broker who shall purchase
         the Property after the termination of this Agreement unless and except
         to the extent such person or entity shall be included on such list so
         submitted to Owner within ten (10) days after termination of this
         Agreement. If within one hundred and eighty (180) days from the date of
         termination of this Agreement, a sale is consummated between Owner any
         person or entity included on such list submitted to Owner, Owner shall
         pay Broker the commission in accordance with Exhibit A. The agreements
         of this Section 5 shall survive the termination of this Agreement.

6.       ADVERTISING AND MARKETING

         Broker shall (a) advertise the Property for sale; (b) prepare a
         marketing plan, brochures and collateral materials for the Property;
         and (c) engage competent consultants (e. g. public relations,
         advertising, etc.) on an "as needed" basis. The content and extent of
         Broker's advertising and marketing activities and the services and
         consultants engaged by Broker in connection with the same shall be
         subject to the prior approval of Owner. Broker's identification
         signage, if any, on or within the Property shall be subject to the
         prior approval of Owner, and Broker shall be responsible for assuming
         that any such signage conforms to

                                       3
<PAGE>

         applicable laws and code and all requirements and restrictions of the
         leases of the Property and any recorded instruments encumbering the
         Property. Upon termination of this Agreement (or sooner, if directed by
         Owner), Broker shall remove its identification signage from the
         Property and fully restore and repair all damage caused by installation
         or removal; and the agreement to do so under this Section 6 shall
         survive the termination of this Agreement. Broker shall be responsible
         for the costs of all marketing, and advertising activities with respect
         to the Property, provided, however, that Owner shall reimburse Broker
         for all such out-of-pocket costs and expenses for which Broker has
         obtained the prior written approval of Owner (provided that in no event
         shall Owner be required to reimburse any such costs or expenses in
         excess of the cumulative amount of $25,000), and excepting, however,
         that Owner shall pay the cost of legal counsel selected and retained by
         Owner in accordance with Section 3 of this Agreement.

7.       NONDISCRIMINATION

         The Property shall be offered without regard to race, color, creed,
         religion, national origin, sex, handicap, or familial status.

8.       REPRESENTATIONS

         Owner makes no representations or warranties regarding the Property or
         the condition of the Property including, but not limited to, the
         presence or absence of asbestos, PCB transformers, or toxic, hazardous
         or contaminated substances in, on or about the Property. Broker is not
         authorized to make any representations or warranties relating to the
         Property unless and except to the extent expressly approved in writing
         by Owner.

9.       INDEMNIFICATION

         Owner shall hold harmless and indemnify Broker against any liability,
         loss or expense incurred by Broker as a result of any misrepresentation
         of Owner or its agents (other than Broker) or the negligence or willful
         misconduct of Owner or its agents (other than Broker). Broker shall
         hold harmless and indemnify Owner against any liability, loss or
         expense incurred by Owner as a result of any misrepresentation of
         Broker, its agents, employees, or the negligence or willful misconduct
         of Broker, its agents, employees, or invitees. The agreements of this
         Section 9 shall survive the termination of this Agreement

10.      STANDARDS

         Broker shall further the interests of Owner in accordance with Owner's
         from time to time requirements, procedures and directions, in
         accordance with the highest professional standards. Broker shall comply
         with all national, federal, state, and municipal laws, regulations,
         codes, ordinances, and orders applicable to Broker and the activities
         of Broker under and in connection with this Agreement.

                                       4
<PAGE>

11.      ASSIGNMENT

         Broker shall not be entitled to assign any rights or to delegate any
         duties or obligations under this Agreement, and any assignment in
         violation of this prohibition shall be void.

12.      GOVERNING LAW

         This Agreement shall be construed according to and governed by the laws
         of the State of Missouri.

13.      ATTORNEY'S FEES

         In connection with any controversy arising out of this Agreement, the
         prevailing party shall be entitled to recover, in addition to costs,
         damages or other relief, its attorney's fees and costs incurred.

14.      MODIFICATIONS

         This Agreement may not be amended, modified or changed, nor shall any
         waiver of any provisions hereof be effective, except only by an
         instrument in writing and signed by the party against whom enforcement
         of any waiver, amendment, change, modification or discharge is sought.

15.      NOTICES

         All notices or other communications required or desired to be given
         hereunder shall be in writing and shall be effective for all purposes
         if hand delivered to the parties at the respective addresses set forth
         above (or such other addresses as the parties may hereafter designate
         in writing) or sent to the respective parties at such addresses by (a)
         certified or registered United States mail, postage prepaid, (b)
         expedited prepaid delivery service, either commercial or United States
         Postal Service, with proof of attempted delivery, or (c) by telecopier
         (with answer back acknowledged and so long as the original of said
         telecopy is mailed the next day). A notice shall be deemed to have been
         given: in the case of hand delivery, at the time of delivery; or in the
         case of mail delivery three (3) days after having been deposited in the
         United States mail postage prepaid and properly addressed; or in the
         case of notice sent via overnight delivery service or telecopy, upon
         receipt.

16.      INDEPENDENT CONTRACTOR

         It is expressly understood and agreed that Broker, as an agent of
         Owner, will act as an independent contractor in the performance of this
         Agreement. The parties hereby agree that nothing in the Agreement shall
         be intended or construed to create an employer-employee relationship, a
         partnership, or a joint venture with respect to the Property or
         otherwise.

                                       5
<PAGE>

17.      SUBORDINATION

         This Agreement shall be subject and subordinate to any mortgage or deed
         of trust now or hereafter encumbering the Property or any part thereof,
         and at the option of the beneficiary of any such mortgage or deed of
         trust or any transferee of title to the Property by virtue of
         foreclosure of the lien of such mortgage or deed of trust (such option
         to be exercised by written notice to Broker) or by transfer in lieu of
         foreclosure (i) Broker shall attorn to and recognize such beneficiary
         or transferee as the successor to Owner of the Property, and Broker
         shall thereupon continue to perform Broker's covenants hereunder or
         (ii) such beneficiary or transferee may terminate this Agreement as of
         the date of notice of foreclosure or transfer. Broker hereby agrees
         that the beneficiary of any such mortgage or deed of trust and the
         transferee of title to the Property shall be intended third party
         beneficiaries of this Agreement entitled to enforce these provisions.

18.      LIENS

         Broker agrees to execute and deliver to Owner, as a condition to any
         payment due to Broker from Owner hereunder, waivers of lien pursuant to
         any statute which may grant Broker the right to a lien on the Property
         as may be requested by Owner in connection with such payment. If Broker
         is to pay any cooperating broker out of funds paid to Broker by Owner,
         Broker shall make no such payments without first obtaining similar
         waivers of lien from such cooperating broker, and the delivery of such
         waivers of lien from such cooperating broker shall, if requested by
         Owner, be a further condition to payment due to Broker. Broker further
         agrees that any and all rights which Broker, and anyone claiming by,
         through or under Broker, may have to a lien under any statute shall be
         at all times subject and subordinate to the lien of any mortgage or
         deed of trust, and Broker further agrees, upon Owner's request, to
         execute and deliver to the holder of any mortgage or deed of trust
         against the Property or any interest therein a subordination agreement
         expressly subordinating any and all such liens rights to the lien of
         such mortgage or deed of trust. The agreements of this Section 18 shall
         survive the termination of this Agreement.

19.      EXCULPATION

         Recourse for the obligations of Owner under this Agreement shall be
         limited to Owner's interest in the Property. The obligations of Owner
         under this Agreement shall not be personally binding on or enforceable
         against Owner, nor shall any resort be had to the assets of any of the
         members, managers, agents, or asset manager of Owner, as the case may
         be, or any of their representatives, partners, members, beneficiaries,
         stockholders, employees or agents.

20.      BINDING EFFECT

         This Agreement shall be binding upon, and shall inure to the benefit
         of, the successors and assigns of the parties hereto, subject to the
         restrictions and limitations of Sections 11 and 19 of this Agreement.

                                       6
<PAGE>

21.      ENTIRE AGREEMENT

         This Agreement constitutes the entire agreement between Broker and
         Owner and supercedes all prior discussions, negotiations and
         agreements, whether oral or written.

                  IN WITNESS WHEREOF, the parties hereto have duly entered into
this Agreement as of the day and year first above written.

OWNER:

EBS BUILDING, L.L.C.

By:      PricewaterhouseCoopers LLP,
         its Manager

         By:      /s/ KEITH F. COOPER
            -----------------------------------------
              Name:   Keith F. Cooper
                   ----------------------------------
              Title:  Partner
                    ---------------------------------

BROKER:

COLLIERS TURLEY MARTIN TUCKER, INC.

By:      /s/ THOMAS E. MURRAY
   --------------------------------------------------
     Name:   Thomas E. Murray
          -------------------------------------------
     Title:  Executive Vice President
           ------------------------------------------

                                       7
<PAGE>

                                    EXHIBIT A

                             SCHEDULE OF COMMISSIONS

<Table>
<Caption>

    Gross Sale Price Received by Owner           Commission
    ----------------------------------           ----------
<S>                                              <C>
A.  Up to and including $38 million              1% of gross sale price
B.  In excess of $38 million                     $380,000 plus 5% of gross sale
                                                 price in excess of $38 million
</Table>

                                       8

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