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                                                                   Exhibit 10.21

                               [FUSION LETTERHEAD]

                                 July 22, 1998

Dear     :

This letter serves as an addendum to your original offer letter of employment
dated July 10, 1996 with the Company.

Your employment with the Company continues to be at will. However, in the event
you are terminated by the Company for a reason other than for cause, you will be
entitled to the following separation benefits:

      (1)   continued payment of your salary at your then current salary rate
            (less applicable withholding), for three months;

      (2)   vesting of fifty percent of your then outstanding stock options; and

      (3)   the right to exercise your right to purchase any options in which
            you are vested for one year after the date of the termination of
            your employment (keeping in mind that if you actually purchase your
            options more than ninety days following the date of the termination
            of your employment you may be precluded from receiving any favorable
            tax treatment currently available under the Stock Option).

For purposes of this Agreement, a termination "for cause" occurs if you are
terminated for any of the following reasons:

            (a)   theft, dishonesty, or falsification of any employment or
                  Company records;
            (b)   conviction of a felony or any act involving moral turpitude;
            (c)   consistent poor performance, as determined by the Board in its
                  sole discretion;
            (d)   improper disclosure of the Company's confidential or
                  proprietary information;
            (e)   any intentional act by you that has a material detrimental
                  effect on the Company's reputation or business; or
            (f)   the Company ceases or fails to continue to do business.

Further, in the event of a Change of Control (as defined in this paragraph) of
the Company, all of the unvested shares subject to your stock option agreement
shall become vested immediately prior to the Change in Control. For purposes of
this Agreement, a "Change of Control" shall mean an "Ownership Change Event" (as
defined in this paragraph) or a series of related Ownership Change Events
(collectively, the "Transaction") wherein the stockholders of the Company
immediately

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before the Transaction do not retain immediately after the Transaction direct or
indirect beneficial ownership of more than fifty percent (50%) of the total
combined voting power of the outstanding voting stock of the Company or the
corporation or corporations to which the assets of the Company were transferred
(the "Transferee Corporation(s)"), as the case may be. For purposes of the
preceding sentence, indirect beneficial ownership shall include, without
limitation, an interest resulting from ownership of the voting stock of one or
more corporations which, as a result of the Transaction, own the Company or the
Transferee Corporation(s), as the case may be, either directly or through one or
more subsidiary corporations. The Board shall have the right to determine
whether multiple sales or exchanges of the voting stock of the Company or
multiple Ownership Change Events are related, and its determination shall be
final, binding and conclusive.

Other than this modification, your letter agreement of July 10, 1996 and any
agreements concerning your stock options shall remain in full force and effect.
Any further modifications to that agreement must be made in writing signed by
both you and the Company. To indicate your acceptance of these modifications,
please sign below.

Best Regards,


/s/ Philip M. Sawyer

Philip Sawyer
President and CEO

Agreed to and accepted


_______________________             Date: __________