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Exhibit 10.106a






                                 April 11, 2003

Mr. Mike Radlovic 330 N. Indian Hill Blvd. Claremont, CA 91711

RE:  STOCK PURCHASE AGREEMENT/RADLOVIC--3,000,000 SHARES OF TRANSTAR COMMON
STOCK

Dear Mike,

Reference is made to 3,000,000  TranStar  System,  Inc. common stock shares (the
"Stock") acquired by Vertical Computer Systems,  Inc. ("Vertical") pursuant to a
certain Stock Purchase Agreement, dated October 14, 2000 (hereinafter the "Stock
Purchase  Agreement"),  between Vertical and TranStar  Systems,  Inc.  (formerly
known as Apollo Industries, Inc. and referred to herein as the "Corporation").

This  letter  will   confirm  the  material   terms  of  the  mutual   agreement
("Agreement")  between you, Michael Radlovic  ("Radlovic") and Vertical whereby,
in  consideration  of a  promissory  note in the  amount of  $250,000  issued by
Radlovic, Vertical shall sell and transfer the Stock to Radlovic.

Vertical and Radlovic hereby agree as follows:

1. This Agreement will not be effective until all of the  stockholders  that are
not a party  to this  transaction  (the  "Non-Purchasing  Stockholder(s)")  have
waived  certain  Stockholder  rights  contained  in  the  Amended   Stockholders
Agreement,  dated October 14, 2000, including the right of first refusal and any
restrictions  concerning  the transfer of the Stock and have  approved such sale
without reservation,  pursuant to the attached waiver (the "Waiver") dated April
11, 2003. All agreements  between the  Corporation and Vertical shall be amended
such that all references to Apollo Industries, Inc. shall be changed to TranStar
Systems, Inc., as applicable.

2. Vertical will  transfer to Radlovic  3,000,000  shares of common stock of the
Corporation  (the  "Stock")  that were  issued  pursuant  to the Stock  Purchase
Agreement,  subject to and effective upon  Radlovic's  execution of a promissory
note (the "2003 Note") on the terms set forth below.

3.  Radlovic  will issue a  promissory  note (the "2003  Note") for a  principal
amount of $250,000,  bearing interest at 10% per annum,  which shall accrue from
the  date of this  agreement  and  shall  include  standard  terms  required  by
Vertical.  All principal and accrued interest under the 2003 Note will be due on
April 11, 2007. In  connection  with the 2003 Note,  Radlovic  shall execute the
Stock Pledge  Agreement and the Security and Loan Agreement  attached  hereto on
terms  acceptable  in  Vertical's   reasonable  judgment  concerning  the  Stock
transferred herein as well as an additional  2,000,000 shares of common stock of
the  Corporation  owned by  Radlovic  (collectively,  the  "Collateral  Stock"),
whereby  Radlovic  shall pledge and reserve the  Collateral  Stock to secure the
2003 Note.




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4. FURTHER  DOCUMENTS.  The parties shall promptly execute any further documents
as reasonably necessary to effectuate the terms of this Agreement, including any
other documents  reasonably  required to perfect Vertical's security interest in
the above-mentioned shares.

5. AUTHORITY.  Each party hereto  represents and warrants that it has full power
and  authority to enter into this  Agreement  and to perform  this  Agreement in
accordance with its terms.

6. GOVERNING LAW. This Agreement shall be construed, interpreted and enforced in
accordance  with the laws of the State of California and shall be subject to the
exclusive jurisdiction and venue of the state and federal courts of Los Angeles,
California, to which the Parties irrevocably agree to submit to.

7.  SUCCESSORS AND ASSIGNS.  This Agreement  shall be binding upon, and inure to
the benefit of, the parties hereto and their respective successors and assigns.

8.  SEVERABILITY.  In the event that any  provision of this  Agreement  shall be
invalid,  illegal  or  otherwise  unenforceable,   the  validity,  legality  and
enforceability  of the  remaining  provisions  shall  in no way be  affected  or
impaired thereby.

9.  AMENDMENT.  This  Agreement  may be amended only in writing  executed by the
parties hereto.

10.  ATTORNEY'S  FEES. In the event of a dispute the  prevailing  party shall be
entitled to be reimbursed for its legal fees,  including attorney fees and court
costs, by the other party.

The parties  hereby  agree to the terms of this  agreement on the date first set
forth above:


ACCEPTED AND AGREED:


VERTICAL COMPUTER SYSTEMS, INC.

--------------------------
Richard Wade, President/CEO


--------------------------
Mike Radlovic, an individual