<PAGE>   1
                                                                   EXHIBIT 10.14

                  [Letterhead of PetroChemNet Holdings, Inc.]



September 30, 1999

Computer Sciences Corporation
266 Second Avenue
Waltham, MA 02451


Gentlemen:

     This letter will evidence our mutual understanding with respect to the
strategic alliance (the "Strategic Alliance") between PetroChemNet Holdings,
Inc., a Delaware corporation ("PCN") and Computer Sciences Corporation, a
Nevada corporation ("CSC").

1.   Initial Purchase of PCN Stock.

     (a)  CSC or one of its subsidiaries will purchase, for an aggregate of $1
          million cash, a number of shares of common stock of PCN which as of
          the date of this letter represents 1.25% of the fully diluted
          outstanding common stock of PCN at a price based on the fully diluted
          common stock of PCN having an aggregate value of $80 million.

     (b)  CSC's investment must be approved by PCN's Board; the Board is
          expected to consider the investment prior to October 6, 1999. PCN will
          provide CSC with written notification of PCN's Board approval.

2.   Commissions for New PCN Business.

     (a)  CSC and PCN have agreed upon a list of prospective PCN customers with
          whom CSC has a relationship and to whom CSC will be authorized to
          market PCN services (the "Listed Prospects"). The list is attached
          hereto and as may be amended by mutual consent.

     (b)  This list will be updated from time to time by mutual agreement, and
          Listed Prospects that are not actively being pursued by CSC within 3
          months of being added to the list will be removed from the list.

     (c)  PCN may either pursue the Listed Prospects in conjunction with CSC or
          individually without CSC, but PCN will provide notice and coordination
          of its activities in pursuit of the Listed Prospects on at least a
          monthly basis.

     (d)  CSC will receive commissions on a monthly basis, equal to 20% of the
          cash realized (commissions from trading activities) by PCN from sales
          of its services to Listed Prospects
<PAGE>   2
         for the preceding month during the 3-year period following the initial
         sale, unless earlier terminated in accordance with paragraphs 5 or 8
         below.


3.   CSC Consulting Services.

     (a) CSC will have the right of first negotiation, but not the obligation,
         to provide consulting services required by PCN in certain specified
         areas, including strategic consulting, marketing, new product
         development, system development management, international, logistics,
         letters of credit and credit enhancement.

     (b) These services will be provided at competitive rates and are subject
         to negotiation of mutually agreeable definitive agreements.

4.   Additional Opportunities.

     (a) CSC and PCN may enter into mutually agreeable additional arrangements
         with respect to co-branded, co-marketed or cross-sold services.

5.   Payments.

     (a) Commissions payable under paragraph 2 above shall be paid in common
         stock of PCN, valued based on the most recent transaction value or
         appraisal until there is a market price established after PCN's initial
         public offering, after which time the price of the common stock will be
         the closing sales price of the common stock at the end of the month in
         which the commissions are earned. No further commissions will be
         payable under paragraph 2 above after CSC is issued $5 million in
         aggregate value of common stock under paragraphs 2, 3 or 4 herein. PCN
         and CSC will renegotiate and extend a mutually agreeable commission
         structure beyond this $5 million aggregate cap by mutual consent and
         amendment to this agreement to reflect CSC's ongoing contributions.

     (b) On a project-by project basis, PCN may, but shall not be obligated to,
         offer CSC the right to receive up to 50% of CSC's consulting fees under
         paragraph 3 above in the form of PCN common stock, and CSC shall not be
         obligated to accept any such stock in lieu of cash. The consulting fees
         will be payable upon the completion of the consulting services in
         accordance with the definitive agreements, and the common stock will be
         valued based on the most recent transaction value or appraisal, except,
         if PCN is a public company at the date of the contract execution of the
         consulting services, the value will be based on the average of the
         closing sales prices of the common stock for the 10 trading days
         immediately preceding the date of contract execution of the consulting
         services, unless agreed otherwise in advance.

     (c) Amounts payable under paragraph 4 above shall be set forth in the
         definitive agreements and may be in the form of common stock of PCN
         valued as set forth in such definitive agreements.

6.   Preferred Provider.

     (a)  During the term of the Strategic Alliance:




                                       2
<PAGE>   3
          (i)  CSC will be the preferred IT systems integrator with whom PCN
               partners, or enters into arrangements for co-branded, co-marketed
               or cross-sold services so long as CSC's rates are competitive and
               its technology and performance are reasonably acceptable to PCN;

          (ii) PCN will be CSC's and its affiliates preferred platform and
               exchange for independent market trading of commodity products
               traded over PCN's system (including initially chemicals, polymers
               and refined oil products) with respect to PCN's direct
               competitors that are set forth from time to time in writing by
               PCN to CSC in whom CSC makes an investment, or with whom CSC
               partners, or enters into arrangements for co-branded, co-marketed
               or cross-sold services. If CSC proposes to make an investment in
               or a strategic alliance for co-branded, co-marketed or cross-sold
               services or otherwise with any competitor of PCN, CSC shall give
               PCN 30 days' prior written notice. If PCN wishes to enter into
               new lines of business in addition to trading of chemicals,
               polymers and refined oil products and wishes to define additional
               direct competitors in which CSC would not make an investment, or
               with whom CSC would not partner, or enter into arrangements for
               co-branded, co-marketed or cross-sold services, then PCN shall
               give CSC 30 days' prior written notice and amend this agreement
               by mutual consent. PCN initially designates such competitors to
               include (but not be limited to) ChemConnect, Commercex and I-2-I,
               e-chemicals, fob.com, Verticalnet, efuel.com, and their
               affiliates that are engaged in directly competing business.

     (b)  CSC and its affiliates will not compete with PCN during the term of
          the Strategic Alliance and for a period of one year after the
          termination of the Strategic Alliance.

7.   Meetings.

     (a)  Carl D. McCutcheon and a senior representative of CSC, who shall
          initially be Chris Davis, shall meet no less than once each calendar
          quarter to discuss opportunities and methods to improve the Strategic
          Alliance.

8.   Term.

     (a)  Either CSC or PCN may terminate the Strategic Alliance at any time
          upon 30 days' prior written notice.

     (b)  Upon termination of the Strategic Alliance:

          (i)  If PCN has not completed its initial public offering, PCN will
               have the option to repurchase all PCN common stock held by CSC at
               a price equal to the appraised value of such shares determined by
               the average of two independent appraisers, one selected by PCN,
               the second selected by CSC, (unless by mutual agreement it is
               determined that a second appraisal is not necessary). The
               appraisal costs shall be shared equally by PCN and CSC;

          (ii) If PCN has completed its initial public offering, PCN shall have
               the option to repurchase all PCN common stock held by CSC at a
               price equal to the average closing price of the common stock for
               the 10 trading days immediately preceding the date of repurchase.
               If PCN chooses not to repurchase the shares of common stock of
               PCN held



                                       3
<PAGE>   4
                by CSC, CSC shall sell not more that 25% of the shares of PCN
                held by it in any subsequent calendar quarter, subject to any
                restrictions imposed by underwriters or securities laws;

          (iii) PCN will continue to pay commissions to CSC pursuant paragraph 2
                above, subject to the limitation in paragraph 5 above, if PCN
                terminates the Strategic Alliance. If CSC terminates the
                Strategic Alliance, PCN will pay commissions to CSC pursuant to
                paragraph 2 above, subject to the limitations in paragraph 5
                above, only for a period of six months after the date of
                termination. Upon termination of the Strategic Alliance, CSC
                will no longer be authorized as a PCN sales channel under
                paragraph 2 above;

          (iv)  CSC will complete any consulting project for PCN previously
                commenced pursuant to paragraph 3 above;

          (v)   CSC and PCN will terminate on an orderly basis all arrangements
                entered into pursuant to paragraph 4 above; and

          (vi)  The provisions of paragraphs 6 (other than paragraph 6(b) which
                shall remain in effect in accordance with its terms) and 7 above
                will cease to apply to CSC and PCN.

9.   Miscellaneous.

     (a)  The Strategic Alliance, this letter and all documentations
          contemplated by this letter shall be governed by the internal law of
          the State of Texas, without regard to any conflict of laws principles.

     (b)  Each of PCN and CSC will bear its own costs and expenses of the
          preparation of the documentation and performance of the obligations
          set forth in this letter.


                                       4
<PAGE>   5
     If this letter correctly sets forth our understanding, please indicate your
acceptance by executing this letter in the space provided below.

This letter agreement shall be effective as of September 30, 1999. CSC agrees
to wire transfer the funds to PCN's designated account to purchase the stock
within 5 business days after notification by PCN of its Board of Directors
approval of this transaction.

                                   Very truly yours,

                                   PETROCHEMNET HOLDINGS, INC.

                                   By /s/ CARL D. McCUTCHEON
                                      -------------------------------------
                                      Carl D. McCutcheon
                                      President and Chief Executive Officer




ACCEPTED AND AGREED TO
THIS 30th day of September, 1999


COMPUTER SCIENCES CORPORATION

By /s/ PAUL T. TUCKER
   ------------------------------
   Paul T. Tucker
   Vice President




                                       5