<PAGE>   1
                                                                   EXHIBIT 10.43


NEITHER THIS WARRANT NOR ANY OF THE SECURITIES ISSUABLE HEREUNDER HAVE BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), AND AS
SUCH MAY NOT BE OFFERED, SOLD, OR OTHERWISE TRANSFERRED, PLEDGED OR
HYPOTHECATED EXCEPT PURSUANT TO A REGISTRATION STATEMENT IN EFFECT WITH RESPECT
TO SUCH WARRANT OR SECURITIES, OR UNLESS SOLD IN FULL COMPLIANCE WITH RULE 144
PROMULGATED UNDER THE ACT OR UNLESS THE COMPANY SHALL RECEIVE AN OPINION FROM
COUNSEL TO HOLDER, REASONABLY SATISFACTORY TO THE COMPANY TO THE EFFECT THAT
SUCH REGISTRATION IS NOT REQUIRED.

THIS WARRANT IS SUBJECT TO THE RESTRICTIONS ON TRANSFER CONTAINED IN ARTICLE IV
HEREOF.


                         WARRANT TO PURCHASE SECURITIES
                            OF HEALTHEON/WEBMD, INC.

         THIS CERTIFIES that, for value received, Healtheon/WebMD Corporation,
a Delaware corporation (the "COMPANY"), hereby grants to Gleacher & Co. LLC or
its registered assigns (the "HOLDER"), the right to purchase up to 706,247
shares of Common Stock, par value $0.0001 per share (the "COMMON STOCK"), of
the Company subject to the terms and conditions set forth herein. This warrant
is hereinafter referred to as the "WARRANT."


                                   ARTICLE I

                              CERTAIN DEFINITIONS

         For all purposes of this Warrant, unless the context otherwise
requires, the following terms shall have the following respective meanings:

         "ACT": the federal Securities Act of 1933, as amended, or any similar
federal statute, and the rules and regulations of the Commission promulgated
thereunder, all as the same shall be in effect at the time.

         "COMMISSION": the Securities and Exchange Commission or any other
federal agency then administering the Act.

         "COMPANY": Healtheon/WebMD Corporation, a Delaware corporation,
located at 400 The Lenox Building, 3399 Peachtree Road, Atlanta, Georgia,
30326, and any other corporation assuming or required to assume the Warrant
pursuant to Article V.

         "EXERCISE PRICE": $8.04 per share.

         "HOLDER": as defined on the first page hereof.

         "LETTER AGREEMENT": Letter Agreement dated January 27, 1999 between
the Company and Gleacher NatWest regarding the provision of financial advisory
services by Gleacher NatWest to the Company.


<PAGE>   2


         "MARKET PRICE": with respect to a share of Common Stock on any
business day: (a) if such security is listed or admitted for trading on any
national securities exchange, the last sale price of such security, regular
way, or the average of the closing bid and asked prices thereof if no such sale
occurred, in each case as officially reported on the principal securities
exchange on which such security is listed, or (b) if not reported as described
in clause (a), the average of the closing bid and asked prices of such security
in the over-the-counter market as shown by the National Association of
Securities Dealers, Inc. Automated Quotation System, or any similar system of
automated dissemination of quotations of securities prices then in common use,
if so quoted, as reported by any member firm of the New York Stock Exchange
selected by the Company, or (c) if not quoted as described in clause (b), the
average of the closing bid and asked prices for such security as reported by
the National Quotation Bureau Incorporated or any similar successor
organization, as reported by any member firm of the New York Stock Exchange
selected by the Company. If such security is quoted on a national securities or
central market system in lieu of a market or quotation system described above,
the closing price shall be determined in the manner set forth in clause (a) of
the preceding sentence if actual transactions are reported and in the manner
set forth in clause (b) of the preceding sentence if bid and asked prices are
reported but actual transactions are not.

         "PERSON": any individual, corporation, partnership, trust,
unincorporated organization and any government, and any political subdivision,
instrumentality or agency thereof.

         "STOCK UNIT": one share of Common Stock, as such stock is constituted
on the date hereof and thereafter the number of shares of Common Stock as shall
result from the adjustments specified in Article V.

         "VESTING DATE": each date on which rights to purchase shares of Common
Stock pursuant to this warrant may vest.

         "WARRANT OFFICE": as defined in Section 3.1.

         "WARRANT SHARES": the shares of Common Stock purchasable by the Holder
upon the exercise of this Warrant.


                                   ARTICLE II

                              EXERCISE OF WARRANT

         2.1 VESTING AND EXERCISABILITY. The right to purchase shares of Common
Stock shall immediately vest and become exercisable on the date hereof. Absent
an adjustment pursuant to the terms of this Warrant, the maximum aggregate
number of shares of Common Stock that may be subject to purchase hereunder
shall be 706,247.

         2.2 METHOD OF EXERCISE. To the extent this Warrant is exercisable from
time to time, to exercise this Warrant, the Holder shall deliver to the Company
at the Warrant Office designated to Section 3.1 (a) a Notice of Exercise
substantially in the form attached hereto as Exhibit A duly executed by the
Holder specifying the number of Warrant Shares to be purchased; (b) payment of
an amount equal to the aggregate Exercise Price for all such Warrant Shares,
which shall be made (i) in cash or by certified or bank cashier's check payable
to the order of the Company, or (ii) by delivery to the Company of that number
of shares of Common Stock having a value computed based upon the Market


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<PAGE>   3


Price, equal to the then applicable Exercise Price multiplied by the number of
Warrant Shares then being purchased, and (c) this Warrant. In the alternative,
this Warrant may be exercised on a net basis, such that, without the exchange
of any funds, the Holder receives that number of Warrant Shares subscribed to
less that number of Warrant Shares having an aggregate value computed based
upon the Market Price equal to the aggregate Exercise Price that would
otherwise have been paid by such Holder for the number of Warrant Shares
subscribed to. The Company shall, as promptly as practicable, and in any event
within five (5) days thereafter, cause to be issued and delivered to the Holder
(or its nominee) or the transferee designated in the Notice of Exercise a
certificate or certificates representing the number of Warrant Shares specified
in the Notice of Exercise. The stock certificate or certificates so delivered
shall be in denominations of shares as my be specified in said notice and shall
be issued in the name of the Holder or such other name as shall be designated
in said notice. At the time of delivery of the certificate or certificates,
appropriate notation shall be made on the Warrant Shares Purchase Schedule
attached to this Warrant designating the number of shares purchased, and this
Warrant shall then be returned to the Holder if this Warrant has been exercised
only in part. The Holder or transferee so designated in the Notice of Exercise
shall be deemed to have become the Holder of such Warrant Shares for all
purposes as of the close of business on the date on which the Notice of
Exercise is delivered to the Warrant Office, provided that an amount equal to
the aggregate Exercise Price and this Warrant shall have also been delivered to
the Company. The Company shall pay all expenses, taxes, (excluding capital
gains and income taxes) and other charges payable in connection with the
preparation, issuance and delivery of stock certificates, except that, in case
stock certificates shall be registered in a name or names other than the name
of the Holder, funds sufficient to pay all stock transfer taxes payable upon
the issuance of stock certificates shall be paid by the Holder promptly upon
the receipt of a written request of the Company therefor.

         2.3 SHARES TO BE FULLY PAID AND NON-ASSESSABLE. All Warrant Shares
issued upon the exercise of this Warrant shall validly issued, fully paid,
non-assessable and free from preemptive rights.

         2.4 NO FRACTIONAL SHARES TO BE ISSUED. The Company shall not be
required upon any exercise of this Warrant to issue to certificate representing
any fraction of a share of Common Stock.

         2.5. LEGEND ON WARRANT SHARES. Each certificate for Warrant Shares
issued upon exercise of this Warrant, unless at the time of exercise such
shares are registered under the Act, shall bear substantially the following
legend (and any additional legend required by any national securities exchanges
upon which such shares may, at the time of such exercise, be listed or under
applicable securities laws):

         "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
         REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"),
         AND AS SUCH MAY NOT BE OFFERED, SOLD, OR OTHERWISE TRANSFERRED,
         PLEDGED OR HYPOTHECATED EXCEPT PURSUANT TO A REGISTRATION STATEMENT IN
         EFFECT WITH RESPECT TO SUCH WARRANT OR SECURITIES, OR UNLESS SOLD IN
         FULL COMPLIANCE WITH RULE 144 PROMULGATED UNDER THE ACT OR UNLESS THE
         COMPANY SHALL RECEIVE AN OPINION FROM COUNSEL TO HOLDER, REASONABLY
         SATISFACTORY TO THE COMPANY TO THE EFFECT THAT SUCH REGISTRATION IS
         NOT REQUIRED."

         Any certificate issued at any time in exchange or substitution for any
certificate bearing such legend (except a new certificate issued upon
completion of a public distribution pursuant to a registration statement under
the Act of the securities represented thereby) shall also bear the above legend
unless, in the opinion of counsel to the Company, the securities represented
thereby need no


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<PAGE>   4


longer be subject to the restrictions on transferability. In addition, the
provisions of Article IV shall be binding upon all subsequent holders of this
Warrant.

         2.6 ACKNOWLEDGMENT OF CONTINUING OBLIGATION. The Company shall, at the
time of any exercise of this Warrant in whole or in part, upon request of the
Holder, acknowledge in writing its continuing obligation to such holder in
respect of any rights to which the Holder shall continue to be entitled after
exercise in accordance with this Warrant; provided, however, that the failure
of the Holder to make any such request shall not affect the continuing
obligation of the Company to the Holder in respect of such rights.


                                  ARTICLE III

                       WARRANT OFFICE; TRANSFER, DIVISION
                           OR COMBINATION OF WARRANTS

         3.1 WARRANT OFFICE. The Company shall maintain an office for certain
purposes specified herein (the "WARRANT OFFICE"), which office shall initially
be the Company's location set forth in Article I hereof, and may subsequently
be such other office of the Company or of any transfer agent of the Common
Stock in the continental United States as to which written notice has
previously been given to all of the Holders of the Warrants.

         3.2 OWNERSHIP OF WARRANT. The Company may deem and treat the Person in
whose name this Warrant is registered as the Holder and owner hereof
(notwithstanding any notations of ownership or writing hereon made by anyone
other than the Company) for all purposes and shall not be affected by any
notice to the contrary, until presentation of this Warrant for registration of
transfer as provided in this Article III.

         3.3 TRANSFER OF WARRANT. The Company agrees to maintain at the Warrant
Office books for the registration of permitted transfers of this Warrant.
Subject to the provisions of Article IV, this Warrant and all rights hereunder
are transferable, in whole or in part, on the books at that office, upon
surrender of this Warrant at that office, together with a written assignment of
this Warrant duly executed by the Holder or his or its duly authorized agent or
attorney and funds sufficient to pay any transfer taxes payable upon the making
of the transfer. Subject to Article IV, upon surrender and payment, the Company
shall execute and deliver a new Warrant in the name of the assignee, noting
thereon the number of Warrant Shares theretofore purchased under this Warrant,
and this Warrant shall promptly be canceled. A warrant may be exercised by a
new Holder for the purchase of shares of Common Stock without having a new
warrant issued.

         3.4 DIVISION OR COMBINATION OF WARRANTS. This Warrant may not be
divided or combined with any other warrant.

         3.5 EXPENSES OF DELIVERY OF WARRANTS. The Company shall pay all
expenses, taxes (other than transfer taxes), and other charges payable in
connection with the preparation, issuance and delivery of new Warrants
hereunder.


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<PAGE>   5


                                   ARTICLE IV

                            RESTRICTION ON TRANSFER

         4.1 RESTRICTIONS ON EXERCISE AND TRANSFER. Notwithstanding any
provisions contained in this Warrant to the contrary, this Warrant shall not be
exercisable or transferable except upon the conditions specified in this
Article IV, which conditions are intended, among other things, to insure
compliance with the provisions of the Act in respect of the exercise or
transfer of the Warrant.

         4.2 OPINION OF COUNSEL. In connection with any exercise or transfer of
this Warrant, the following provisions shall apply:

                  (a) If in the written opinion of counsel to the Holder
delivered to the Company (which opinion and counsel must be reasonably
acceptable to the Company), proposed exercise or transfer of this Warrant may
be effected without registration of this Warrant or the Common Stock issuable
hereunder under the Act, the Holder shall be entitled to exercise or transfer
this Warrant as proposed. In no event shall the Company be obligated (i) to
effect a registration under the Act or any state securities law so as to permit
the proposed exercise or transfer of this Warrant or (ii) to qualify to do
business or to file a general consent to service of process in any state or
other jurisdiction.

                  (b) If in the opinion of such counsel, the proposed exercise
or transfer of this Warrant may not be effected without registration of this
Warrant under the Act, the Holder shall not be entitled to exercise or transfer
this Warrant until registration is effective or until exercise or transfer may
be effected without registration, in the opinion of such counsel as set forth
in Section 4.2(a) above.


                                   ARTICLE V

                                  ADJUSTMENTS

         5.1 ADJUSTMENTS TO NUMBER OF STOCK UNITS. The number of shares of
Common Stock comprising a Stock Unit shall be subject to adjustment from time
to time as set forth in this Section 5.1.

                  (a) STOCK DIVIDENDS, SUBDIVISIONS AND COMBINATION. In case at
any time or from time to time the Company shall: (i) take a record of the
holders of its Common Stock of any series for the purpose of entitling them to
receive a dividend payable in, or other distribution of, Common Stock, or (ii)
subdivide its outstanding shares of Common Stock into a larger number of shares
of Common Stock, or (iii) combine its outstanding shares of Common Stock into a
smaller number of shares of Common Stock; then the number of shares of Common
Stock comprising a Stock Unit immediately after the happening of any such event
shall be adjusted so as to consist of the number of shares of Common Stock that
a record holder of the number of shares of Common Stock comprising a Stock Unit
immediately prior to the happening of such event would own or be entitled to
receive after the happening of such event. The adjustments required by this
subsection shall be made whenever and as often as any specified event requiring
an adjustment shall occur.

                  (b) CERTAIN OTHER DIVIDENDS AND DISTRIBUTIONS. In case at any
time or from time to time the Company shall take a record of the holders of its
Common Stock for the purpose of entitling


                                       5
<PAGE>   6


them to receive any dividend or other distribution of: (i) cash (other than a
cash distribution made as a dividend payable out of the net earnings or net
profits of the Company realized during the year of such distribution or the
last preceding year and accumulated net earnings or net profits of the Company
from the date hereof to the time of such distribution, computed in accordance
with generally accepted accounting principles employed by the Board of
Directors of the Company for purposes of financial reports to shareholders of
the Company); or (ii) any evidences of its indebtedness, any shares of its
stock or any other securities or property of any nature whatsoever (other than
cash); then at least five (5) business days prior to the record date to
determine shareholders entitled to receive such dividend or distribution, the
Company shall give notice of such proposed dividend or distribution to the
Holder for the purpose of enabling the Holder to exercise the same, and thereby
participate in such dividend or distribution.

                  (c) OTHER PROVISIONS APPLICABLE TO ADJUSTMENT UNDER THIS
SECTION. The following provisions shall be applicable to the making of
adjustments of the number of shares of Common Stock comprising a Stock Unit
hereinbefore provided for in this Section 5.1:

                           (i) When Adjustments to be Made. The adjustments
required by the preceding subsections of this Section 5.1 shall be made
whenever and as often as any specified event requiring an adjustment shall
occur, except that no adjustment of the number of shares of Common Stock
comprising a Stock Unit that would otherwise be required shall be made (except
in the case of a subdivision or combination of shares of the Common Stock, as
provided for in Subsection 5.1 (a)) unless and until such adjustment, either by
itself or with other adjustments not previously made, adds or subtracts at
least 1/20th of a share to or from the number of shares of Common Stock
comprising a Stock Unit immediately prior to the making of such adjustment. Any
adjustment representing a change of less than such minimum amount (except as
aforesaid) shall be carried forward and made as soon as such adjustment,
together with other adjustments required by this section and not previously
made, would result in a minimum adjustment. For the purpose of any adjustment,
any specified event shall be deemed to have occurred at the close of business
on the date of its occurrence.

                           (ii) Fractional Interests. In computing adjustments
under this section, fractional interests in Common Stock shall be taken into
account to the nearest one-thousandth of a share.

                           (iii) When Adjustment Not Required - Abandonment of
Plan for Dividend and the Like. If the Company shall take a record of the
holders of its Common Stock for the purpose of entitling them to receive a
dividend or distribution or subscription or purchase rights and shall,
thereafter and before the distribution to shareholders thereof, legally abandon
its plan to pay or deliver such dividend, distribution, subscription or
purchase rights, then thereafter no adjustment shall be required by reason of
the taking of such record and any such adjustment previously made in respect
thereof shall be rescinded and annulled.

                  (d) REORGANIZATION, RECLASSIFICATION, MERGER, CONSOLIDATION
OR DISPOSITION OF ASSETS. In case the Company shall reorganize its capital,
reclassify its capital stock, merge or consolidate into another corporation,
then the number of shares of stock purchasable upon exercise of this Warrant
shall be adjusted to consist of the number of shares of stock or other
securities that a record holder of the number of shares of Common Stock
purchasable upon exercise of this Warrant immediately prior to such event would
own or be entitled to receive immediately after such event.

         5.2. NOTICE TO HOLDER. Whenever the Company takes any action that
causes the


                                       6
<PAGE>   7


composition of a Stock Unit to change under Sections 5.1(a) through
5.1(d), the Company shall provide the Holder with written notice of such change
and the number of Warrant Shares for which this Warrant is or will become
exercisable. Such notice will be provided not more than ten days after any such
action has occurred.


                                   ARTICLE VI

                      ADDITIONAL NOTICES TO WARRANT HOLDER

         In addition to any other notice required hereunder, the Company shall
provide the Holder with a copy of any notice that the Company is required to
provide those Persons holding shares of Common Stock on the same date such
persons receive such notice.


                                  ARTICLE VII

                                   EXPIRATION

         Rights to purchase shares under this Warrant shall expire and may not
be exercised after January 27, 2004, with respect to 84,562 shares, and January
27, 2005, with respect to 621,685 shares.


                                  ARTICLE VIII

                        CERTAIN COVENANTS OF THE COMPANY

         The Company has taken all action necessary to authorize the issuance
of this Warrant and the issuance of shares of Common Stock upon exercise
hereof. The Company covenants and agrees that it will reserve and set apart and
have at all times, free from preemptive rights, a number of shares of
authorized but unissued Common Stock or other securities deliverable upon the
exercise of this Warrant from time to time sufficient to enable it at any time
to fulfill all its obligations hereunder.


                                   ARTICLE IX

                                 MISCELLANEOUS

         9.1. ENTIRE AGREEMENT. This Warrant and the Letter Agreement contain
the entire agreement between the Holder and the Company with respect to the
purchase of the Warrant Shares and supersede all prior arrangements or
understandings with respect thereto.

         9.2. WAIVER AND AMENDMENT. Any term or provision of this Warrant may
be waived at any time by the party that is entitled to the benefits thereof,
and any term or provision of this Warrant may be amended or supplemented at any
time by agreement of the holder hereof and the Company, except that any waiver
of any term or condition, or any amendment or supplementation, of this Warrant
must be in writing. A waiver of any breach or failure to enforce any of the
terms or conditions of this Warrant shall not in any way affect, limit or waive
a party's rights hereunder at any time to enforce strict compliance thereafter
with any term or condition of this Warrant. In the event this Warrant is ever


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<PAGE>   8


divided and held by more than one person, the "Holder" for such purposes shall
mean the holders of a majority of the Warrant Shares.

         9.3. ILLEGALITY. In the event that any one or more of the provisions
contained in this Warrant shall be determined to be invalid, illegal or
unenforceable in any respect for any reason, the validity, legality and
enforceability of any such provision in any other respect and the remaining
provisions of this Warrant shall not, at the election of the party for whom the
benefit of the provision exists, be in any way impaired.

         9.4. FILING OF WARRANT. A Copy of this Warrant shall be filed in the
records of the Company.

         9.5 NOTICE. Any notice or other document required or permitted to be
given or delivered to the Holder shall be delivered personally, or sent by
certified or registered mail, to the Holder at the 1ast address shown on the
books of the Company maintained at this Warrant Office for the registration of
the Warrant or at any more recent address of which any Holder shall have
notified the Company in writing. Any notice or other document required or
permitted to be given or delivered to the Company shall be delivered at, or
sent by certified or registered mail to, the Warrant Office, attention: Chief
Executive Officer, or such other address within the United States of America as
shall have been finished by the Company to the Holder hereof.

         9.6 LIMITATION OF LIABILITY; NOT SHAREHOLDERS. No provision of this
Warrant shall be construed as confirming upon the Holder the right to vote,
consent, receive dividends, or receive notice other than as herein expressly
provided in respect of meetings of shareholders for the election of directors
of the Company or any other matter whatsoever as a shareholder of the Company.
No provision hereof, in the absence of affirmative action by the Holder to
purchase Warrant Shares, and no enumeration herein of the rights or privileges
of the Holder, shall give rise to any liability of such Holder for the purchase
price of any Warrant Shares or as a shareholder of the Company, whether such
liability is asserted by the Company or by the creditors of the Company.

         9.7 LOSS, DESTRUCTION, ETC. OF WARRANT. Upon receipt of evidence
satisfactory to the Company of the loss, theft, mutilation or destruction of
the Warrant, and in the case of any such loss, theft or destruction, upon
delivery of a bond of indemnity in such firm and amount shall be reasonably
satisfactory to the Company, or in the event of such mutilation, upon surrender
and cancellation of the Warrant, the Company shall make and deliver a new
warrant, of like tenor, in lieu of such lost, stolen, destroyed or mutilated
Warrant. Any Warrant issued under the provisions of this Section 9.7 in lieu of
any Warrant alleged to be lost, destroyed or stolen, or in lieu of any
mutilated Warrant, shall constitute an original contractual obligation on the
part of the Company.


                      [SIGNATURES FOLLOW ON THE NEXT PAGE]


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<PAGE>   9


         IN WITNESS WHEREOF, the Company has caused this Warrant to be signed
in its name by its Chief Executive Officer and its corporate seal to be
impressed hereon as of the 9th day of March, 2000.



<TABLE>
<S>                                                     <C>
[CORPORATE SEAL]                                        HEALTHEON/WEBMD CORPORATION


Attest:


By:   /s/ L. Scott Askins                               By:      /s/ K. Robert Draughon
   ------------------------------------                    ------------------------------------
      Name:    L. Scott Askins                          Name:    K. Robert Draughon
      Title:   Assistant General Counsel                Title:   Executive Vice President
</TABLE>


                                       9
<PAGE>   10


<TABLE>
<CAPTION>
<S>                           <C>                             <C>
NO. OF SHARES PURCHASED             DATE OF PURCHASE          NOTATION BY COMPANY OFFICER

-----------------------       --------------------------      ---------------------------

-----------------------       --------------------------      ---------------------------

-----------------------       --------------------------      ---------------------------

-----------------------       --------------------------      ---------------------------

-----------------------       --------------------------      ---------------------------

-----------------------       --------------------------      ---------------------------

-----------------------       --------------------------      ---------------------------

-----------------------       --------------------------      ---------------------------
</TABLE>


<PAGE>   11


                                   EXHIBIT A
                                   TO WARRANT

                               NOTICE OF EXERCISE


Dated:______________


         The undersigned hereby irrevocably elects to exercise its right to
purchase ______ shares of the Common Stock, par value $0.0001 per share, of
Healtheon/WebMD Corporation, such right being pursuant to a Warrant dated
__________ , 2000, as issued to Gleacher & Co. LLC, for up to 706,247 shares of
such Common Stock, and (i) remits herewith the sum of $_______ in payment for
same in accordance with said warrant or (ii), in accordance with Section 2.2 of
the Warrant, elects to receive such number of shares by having credited to the
undersigned the Market Value (as such term is defined in the Warrant) of a
sufficient number of additional shares of Common Stock for which the Warrant
could otherwise be exercised such that such Market Value equals the Exercise
Price for such shares of Common Stock.



INSTRUCTIONS FOR REGISTRATION OF STOCK


Name



    --------------------------------------------------------
                (Please typewrite or print in block letters)


Address

       -----------------------------------------------------


Signature:

          --------------------------------------------------


Shares Heretofore Purchased Under Warrant:

    --------------------------------------------------------