<PAGE>
                                                                 EXHIBIT 10.4(b)

                              [AspenBio Letterhead]

                                 March __, 2002



Gregory Pusey
President
Cambridge Holdings, Ltd.
106 S. University Blvd. Unit 14
Denver, CO  80209

Re:     Consulting Agreement by and between AspenBio, Inc. (the "Company") and
        Cambridge Holdings, Ltd. dated December 28, 2001 (the "Consulting
        Agreement")


Dear Greg:

        Section 1 of the Consulting Agreement provides that the Consulting
Agreement may be terminated by the mutual agreement of the parties. Because the
Company considers all of the terms of the Consulting Agreement to have been
fulfilled to its satisfaction, the Company proposes that the Consulting
Agreement hereby terminate effective as of the date indicated below. In
addition, the Company proposes that the risk of forfeiture provided for in
Section 3 of the Consulting Agreement shall be lifted as of the same date.

        Please indicate your acceptance of the proposals in this letter by
signing in space provided below.

                                            Very truly yours,

                                            ASPENBIO, INC.


                                            Roger Hurst
                                            President


AGREED AND ACCEPTED EFFECTIVE THIS __ DAY OF MARCH, 2002:


-------------------------
Gregory Pusey
President
Cambridge Holdings, Ltd.






