<PAGE>

                                                                   EXHIBIT 10.15

January 18, 2001



Mr. John Gregitis
305 St. Davids Road
Wayne, PA  19087

Dear John:

It is with pleasure that I offer you the position of Senior Vice President -
Global Sales Operations leader the sales operations of our Life Sciences
division.  This is a critical position in our plans and is the launching point
for much of our expected growth.  We have decided to focus our sales energies
and upgrade both the capacity and skills of our sales units.  We need a dynamic,
experienced leader to drive this business.  We believe you are that leader.
Your combination of sales management experience, presence, and leadership skills
are exactly what this operation needs to get on track and reach is potential.

In this position you will be responsible for all operating results, tactical
programs and strategic direction for sales operations.  You will also be
expected to actively participate in the strategic planning, product planning and
business policy activities of ESPS worldwide.

ESPS is positioned for exceptional success as we leverage our world-class
customer base, our technology and our other assets.  We need to add skilled,
exceptional leaders to our management team to help us take advantage of our
opportunities.  Your addition to our leadership team will greatly enhance our
ability to reach our potential.

We hope this offer demonstrates our sincere desire that you join the ESPS team.
We look forward to the exceptional contributions that we know you will bring to
our team.

Sincerely,



Norman E. Corn.
Executive Vice President and General Manager
ESPS Life Sciences


Attachment
<PAGE>

Employment Offer
John Gregitis


Position:           Senior Vice President
                    ESPS Life Sciences Global Sales & Marketing

Annual Salary:      $190,000.00

Incentive Pay:      $210,000.00 at plan (pro-rated for FY '01)
                    We will mutually develop the incentive plan which will be
                    based on the expected operating results of the sales unit.
                    The plan will consist of a commission element as well as a
                    senior management bonus element. You will receive no less
                    than $210,000.00 (full year basis) on the achievement of the
                    expected operating results of the sales unit (commission)
                    and the expected operating results of the Company (senior
                    management bonus). You will also have the opportunity to
                    earn more based on the overachievement of the expected
                    operating results of the sales unit.
                    Your incentive plan will be based on both quarterly and
                    annual operating results and will be paid quarterly. It will
                    be pro-rated in FY '01. You will be paid a draw guarantee of
                    $48,000 for your first year ($4,000 per month).

Stock Options:      You will be awarded 200,000 options under the ESPS Stock
                    Option Program upon your start date. The Options will be
                    priced based on the ESPS share price at the close of your
                    first day of employment. Vesting will be 30% after 12 months
                    and the remaining 70% according to the ESPS Vesting Schedule
                    (remainder quarterly over 3 years).

Signing Bonus:      You will receive a $30,000 signing bonus to be paid in three
                    increments:
                         $10,000 after 30 days
                         $10,000 after 90 days
                         $10,000 after 180 days

Severance:          You will participate in the management severance program.
                    You will receive no less than 6 months pay for termination
                    for reasons other than cause. Should a change of control
                    occur, you will receive 12 months pay and one-half your
                    bonus for termination for reasons other than cause, within
                    one year of the change. This is a mutual program that
                    requires that you also give 1-month notice if you intend to
                    leave ESPS.

Other Benefits:     You will be eligible for all employee benefit programs.

Car Allowance:      $500 per month net.



Agreed:   /s/ John Gregitis      February 1, 2001

          John Gregitis                Date

This offer is contingent upon successful completion of the appropriate reference
checks.