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                                                                   EXHIBIT 10.50

                           MEDICAL MANAGER CORPORATION
                            669 RIVER DRIVE, CENTER 2
                       ELMWOOD PARK, NEW JERSEY 07407-1361

                                                               September 5, 2000

Mr. Michael A. Singer

Dear Mickey:

                  Reference is made to the Employment Agreement dated as of May
16, 1999 (the "Employment Agreement"), by and between Medical Manager
Corporation, a Delaware corporation (the "Company"), and you. Reference is also
made to the Stock Option Agreement dated as of June 5, 2000 between the Company
and you, pursuant to which you were granted an option (the "Additional Option")
to purchase 450,000 shares of the Company's common stock.

                  A.       For purposes of the Employment Agreement, your "base
salary" is hereby increased from $250,000 to $450,000, except that such increase
shall not be effective for purposes of determining your base salary continuation
under Section 5.5 of the Employment Agreement in the event that (x) (i) you
resign pursuant to clause 6 of the definition of "Good Reason" set forth in the
Employment Agreement and (ii) the "Change in Control" referred to in such clause
6 results from the transactions contemplated by, in connection with or as a
result of the Agreement and Plan of Merger dated February 13, 2000 between
Healtheon/WebMD Corporation, a Delaware corporation, and the Company, as amended
by Amendment No. 1 thereto dated as of June 18, 2000 (the "Merger Agreement") or
(y) you resign pursuant to clause (1) or (4) of the definition of "Good Reason"
as a result of a Permitted Status Change (as defined below). For purposes of
this letter agreement, a "Permitted Status Change" is (a) a reduction in your
title, position or responsibilities at or following the Effective Time (as
defined in the Merger Agreement) provided you are the most senior executive
officer of Medical Manager Health Systems, Inc., a Delaware corporation, and
Medical Manager Research and Development Inc., a Florida corporation, or (b)
your being required to report at or following the Effective Time to Martin J.
Wygod, Marvin P. Rich or, for so long as Martin J. Wygod is Co-Chief Executive
Officer of the Surviving Corporation (as defined in the Merger Agreement),
Jeffrey T. Arnold (in his capacity as Co-Chief Executive Officer of the
Surviving Corporation).

                  B.       For purposes of Sections 4(b) and (d) and 5 of the
Employment Agreement, the Additional Option shall be treated in the same manner
as the "New Option",


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except that, with respect to the Additional Option, (i) the transactions
contemplated by the Merger Agreement (including, without limitation, any change
in the composition of the Company's Board of Directors) shall not constitute a
"Change in Control" and (ii) a Permitted Status Change shall not constitute
"Good Reason" or a reduction in your title or responsibilities.

                  The foregoing amendments to the Employment Agreement shall be
effective as of the date hereof. All other provisions of the Employment
Agreement shall continue in full force and effect.


                                    MEDICAL MANAGER CORPORATION


                                    By:  /s/ Charles A. Mele
                                       -----------------------------
                                    Name:  Charles A. Mele
                                    Title: Executive Vice President-
                                             General Counsel
Accepted and Agreed:


    /s/ Michael A. Singer
----------------------------
Michael A. Singer


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