<PAGE>   1
                                                                        Ex - 4.3

THIS WARRANT AND THE SHARES ISSUABLE HEREUNDER HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED, AND MAY NOT BE SOLD, PLEDGED, OR
OTHERWISE TRANSFERRED WITHOUT AN EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT
OR PURSUANT TO RULE 144 OR AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE
CORPORATION AND ITS COUNSEL, THAT SUCH REGISTRATION IS NOT REQUIRED.

                            WARRANT TO PURCHASE STOCK

Corporation: NovaLink USA Corporation, a Delaware corporation
Number of Shares: Set Forth Below
Class of Stock: common, $.001 par value (the "Common Stock")
Initial Exercise Price: $0.01 per share
Issue Date:  July 18, 1997
Expiration Date:  July 17, 2002

     THIS WARRANT CERTIFIES THAT, for the agreed upon value of $1.00 and for
other good and valuable consideration, SILICON VALLEY BANK ("Holder") is
entitled to purchase the Shares (as defined below) of NovaLink USA Corporation
(the "Company") at an exercise price per Share of $0.01 (the "Warrant Price"),
subject to the provisions and upon the terms and conditions set forth in this
Warrant.

ARTICLE 1. EXERCISE.

          1.1  METHOD OF EXERCISE. Holder may exercise this Warrant by
delivering a duly executed Notice of Exercise in substantially the form attached
as APPENDIX 1 to the principal office of the Company. Unless Holder is
exercising the conversion right set forth in Section 1.2, Holder shall also
deliver to the Company a check for the aggregate Warrant Price for the Shares
being purchased.

          1.2  CONVERSION RIGHTS. In lieu of exercising this Warrant as
specified in Section 1.1, Holder may from time to time convert this Warrant, in
whole or in part, into a number of Shares determined by dividing (a) the
aggregate fair market value of the Shares or other securities otherwise issuable
upon exercise of this Warrant minus the aggregate Warrant Price of such Shares
by (b) the fair market value of one Share. The fair market value of the Shares
shall be determined pursuant to Section 1.4.

          1.3  SHARES. (a) Subject to adjustment as set forth in Article 2, the
Holder shall be entitled to purchase the number of fully paid and nonassessable
shares of Common Stock of the Company (the "Shares") pursuant to this Warrant
that is equal to $25,000.00 divided by the sales price per share of Common Stock
(or the sales price per share of any stock of the Company that is convertible
into Common Stock on an equal share for share basis) issued in connection with
next equity issuance by the Company after the issue date of this Warrant in
which the Company receives aggregate minimum of $1,000,000.00 in exchange for
such equity (an "Equity Issuance") in an arms length transaction. For example,
if the sales price per share of Common Stock in the next Equity Issuance is
$2.00, then the number of Shares that the Holder may purchase pursuant to this
Warrant would be 12,500 (25,000 divided by 2.00).

               (b)  Subject to adjustment as set forth in Article 2, in the
event that an Equity Issuance does not occur within ninety (90) days from the
issue date of this Warrant, then the number of Shares that may be purchased
pursuant to this Warrant shall be the greater of (i) 25,000, or (ii) the number
that is equal to $25,000 divided by the sales price per share of Common Stock
(or the sales price


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per share of any stock of the company that is convertible into Common Stock on
an equal share for share basis) issued in connection with next Equity Issuance.

               (c)  The Company shall give the Holder at least ten (10) days
prior written notice of the proposed closing date of the next Equity Issuance.
The Company shall give the Holder written notice immediately after the closing
of the next Equity Issuance setting forth (i) the sales price per share of
Common Stock (or the sales price per share of any stock of the Company that is
convertible into Common Stock on an equal share for share basis)issued in
connection with such Equity Issuance, (ii) the class and number of shares of
stock of the Company issued in connection with such Equity Issuance, (iii) the
closing date of such Equity Issuance, and (iv) the number of Shares that the
Holder may purchase pursuant to this Warrant calculated in accordance with
Section 1.3(a) or 1.3(b), as the case may be.

          1.4  FAIR MARKET VALUE. If the Shares are traded in a public market,
the fair market value of the Shares shall be the closing price of the Shares (or
the closing price of the Company's stock into which the Shares are convertible)
reported for the business day immediately before Holder delivers its Notice of
Exercise to the Company. If the Shares are not traded in a public market, the
Board of Directors of the Company shall determine fair market value in its
reasonable good faith judgment. The foregoing notwithstanding, if Holder advises
the Board of Directors in writing that Holder disagrees with such determination,
then the Company and Holder shall promptly agree upon a reputable investment
banking firm to undertake such valuation. If the valuation of such investment
banking firm is greater than that determined by the Board of Directors, then all
fees and expenses of such investment banking firm shall be paid by the Company.
In all other circumstances, such fees and expenses shall be paid by Holder.

          1.5  DELIVERY OF CERTIFICATE AND NEW WARRANT. Promptly after Holder
exercises or converts this Warrant, the Company shall deliver to Holder
certificates for the Shares acquired and, if this Warrant has not been fully
exercised or converted and has not expired, a new Warrant representing the
Shares not so acquired.

          1.6  REPLACEMENT OF WARRANTS. On receipt of evidence reasonably
satisfactory to the Company of the loss, theft, destruction or mutilation of
this Warrant and, in the case of loss, theft or destruction, on delivery of an
indemnity agreement reasonably satisfactory in form and amount to the Company
or, in the case of mutilation, on surrender and cancellation of this Warrant,
the Company at its expense shall execute and deliver, in lieu of this Warrant, a
new warrant of like tenor.

          1.7  REPURCHASE ON SALE, MERGER, OR CONSOLIDATION OF THE COMPANY.

               1.7.1.    "ACQUISITION". For the purpose of this Warrant,
"Acquisition" means any sale, license, or other disposition of all or
substantially all of the assets of the Company, or any reorganization,
consolidation, or merger of the Company where the holders of the Company's
securities before the transaction beneficially own less than 50% of the
outstanding voting securities of the surviving entity after the transaction.

               1.7.2.    ASSUMPTION OF WARRANT. Upon the closing of any
Acquisition the successor entity shall assume the obligations of this Warrant,
and this Warrant shall be exercisable for the same securities, cash, and
property as would be payable for the Shares issuable upon exercise of the
unexercised portion of this Warrant as if such Shares were outstanding on the
record date for the Acquisition and subsequent closing. The Warrant Price shall
be adjusted accordingly.

               1.7.3.    PURCHASE RIGHT. Notwithstanding the foregoing, at the
election of Holder, the Company shall purchase the unexercised portion of this
Warrant for cash upon the closing of any Acquisition for an amount equal to (a)
the fair market value of any consideration that would have


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been received by Holder in consideration of the Shares had Holder exercised the
unexercised portion of this Warrant immediately before the record date for
determining the shareholders entitled to participate in the proceeds of the
Acquisition, less (b) the aggregate Warrant Price of the Shares, but in no event
less than zero.



ARTICLE 2. ADJUSTMENTS TO THE SHARES.

          2.1  STOCK DIVIDENDS, SPLITS, ETC. If the Company declares or pays a
dividend on its Common Stock (or the Shares if the Shares are securities other
than Common Stock) payable in Common Stock, or other securities, subdivides the
outstanding Common Stock into a greater amount of Common Stock, or, if the
Shares are securities other than Common Stock, subdivides the Shares in a
transaction that increases the amount of Common Stock into which the Shares are
convertible, then upon exercise of this Warrant, for each Share acquired, Holder
shall receive, without cost to Holder, the total number and kind of securities
to which Holder would have been entitled had Holder owned the Shares of record
as of the date the dividend or subdivision occurred.

          2.2  RECLASSIFICATION, EXCHANGE OR SUBSTITUTION. Upon any
reclassification, exchange, substitution, or other event that results in a
change of the number and/or class of the securities issuable upon exercise or
conversion of this Warrant, Holder shall be entitled to receive, upon exercise
or conversion of this Warrant, the number and kind of securities and property
that Holder would have received for the Shares if this Warrant had been
exercised immediately before such reclassification, exchange, substitution, or
other event. Such an event shall include any automatic conversion of the
outstanding or issuable securities of the Company of the same class or series as
the Shares to Common Stock pursuant to the terms of the Company's Articles of
Incorporation upon the closing of a registered public offering of the Company's
Common Stock. The Company or its successor shall promptly issue to Holder a new
Warrant for such new securities or other property. The new Warrant shall provide
for adjustments which shall be as nearly equivalent as may be practicable to the
adjustments provided for in this Article 2 including, without limitation,
adjustments to the number of securities or property issuable upon exercise of
the new Warrant. The provisions of this Section 2.2 shall similarly apply to
successive reclassifications, exchanges, substitutions, or other events.

          2.3  INTENTIONALLY OMITTED

          2.4  INTENTIONALLY OMITTED

          2.5  NO IMPAIRMENT. The Company shall not, by amendment of its
Articles of Incorporation or through a reorganization, transfer of assets,
consolidation, merger, dissolution, issue, or sale of securities or any other
voluntary action, avoid or seek to avoid the observance or performance of any of
the terms to be observed or performed under this Warrant by the Company, but
shall at all times in good faith assist in carrying out of all the provisions of
this Article 2 and in taking all such action as may be necessary or appropriate
to protect Holder's rights under this Article against impairment.

          2.6  FRACTIONAL SHARES. No fractional Shares shall be issuable upon
exercise or conversion of the Warrant and the number of Shares to be issued
shall be rounded down to the nearest whole Share. If a fractional share interest
arises upon any exercise or conversion of the Warrant, the Company shall
eliminate such fractional share interest by paying Holder amount computed by
multiplying the fractional interest by the fair market value of a full Share.



ARTICLE 3. REPRESENTATIONS AND COVENANTS OF THE COMPANY.


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          3.1  REPRESENTATIONS AND WARRANTIES. The Company hereby represents and
warrants to the Holder as follows:

               (a)  All Shares which may be issued upon the exercise of the
purchase right represented by this Warrant, and all securities, if any, issuable
upon conversion of the Shares, shall, upon issuance, be duly authorized, validly
issued, fully paid and nonassessable, and free of any liens and encumbrances
except for restrictions on transfer provided for herein or under applicable
federal and state securities laws.

               (b)  The authorized capital stock of the Company consists of
20,000,000 shares, consisting of 17,000,000 shares of Common Stock, 1,000,000
shares of Preferred Class A Convertible Stock, $.01 par value, and 2,000,000
shares of undesignated preferred stock. Schedule 3.1(b) sets forth all of the
outstanding shares of Common Stock and outstanding options, warrants,
convertible securities, convertible debentures, and rights to acquire, subscribe
for, and/or purchase any Common Stock and/or other capital stock of the Company
or any securities or debentures convertible into or exchangeable for Common
Stock and/or other capital stock of the Company.

               (c)  The Company has reserved for issuance pursuant to this
Warrant not less than 25,000 shares of the Common Stock of the Company, and the
Company covenants that it shall at all times cause to be reserved and kept
available out of its authorized and unissued shares of Common Stock of the
Company such number of shares of Common Stock as will be sufficient to permit
the exercise in full of this Warrant,

          3.2  NOTICE OF CERTAIN EVENTS. If the Company proposes at any time (a)
to declare any dividend or distribution upon its Common Stock, whether in cash,
property, stock, or other securities and whether or not a regular cash dividend;
(b) to offer for subscription pro rata to the holders of any class or series of
its stock any additional shares of stock of any class or series or other rights;
(c) to effect any reclassification or recapitalization of Common Stock; (d) to
merge or consolidate with or into any other corporation, or sell, lease,
license, or convey all or substantially all of its assets, or to liquidate,
dissolve or wind up; or (e) offer holders of registration rights the opportunity
to participate in an underwritten public offering of the company's securities
for cash, then, in connection with each such event, the Company shall give
Holder (1) at least 20 days prior written notice of the date on which a record
will be taken for such dividend, distribution, or subscription rights (and
specifying the date on which the holders of Common Stock will be entitled
thereto) or for determining rights to vote, if any, in respect of the matters
referred to in (c) and (d) above; (2) in the case of the matters referred to in
(c) and (d) above at least 20 days prior written notice of the date when the
same will take place (and specifying the date on which the holders of Common
Stock will be entitled to exchange their Common Stock for securities or other
property deliverable upon the occurrence of such event); and (3) in the case of
the matter referred to in (e) above, the same notice as is given to the holders
of such registration rights.

          3.3  INFORMATION RIGHTS. So long as the Holder holds this Warrant
and/or any of the Shares, the Company shall deliver to the Holder (a) promptly
after mailing, copies of all notices or other written communications to the
shareholders of the Company, (b) within ninety (90) days after the end of each
fiscal year of the Company, the annual audited financial statements of the
Company certified by independent public accountants of recognized standing and
(c) such other financial statements required under and in accordance with any
loan documents between Holder and the Company, then within forty-five (45) days
after the end of each of the first three quarters of each fiscal year, the
Company's quarterly, unaudited financial statements.

          3.4  REGISTRATION UNDER SECURITIES ACT OF 1933, AS AMENDED. The
Company agrees that the Shares or, if the Shares are convertible into Common
Stock of the Company, such Common Stock, shall be subject to the registration
rights set forth in that certain Registration Rights Agreement, dated as of the
date of this Warrant, by and between Holder and the Company.


<PAGE>   5


ARTICLE 4. MISCELLANEOUS.

          4.1  TERM. This Warrant is exercisable, in whole or in part, at any
time and from time to time on or before the Expiration Date set forth above.

          4.2  LEGENDS. This Warrant and the Shares (and the securities
issuable, directly or indirectly, upon conversion of the Shares, if any) shall
be imprinted with a legend in substantially the following form:

     THIS SECURITY HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
     AMENDED, AND MAY NOT BE SOLD, PLEDGED OR OTHERWISE TRANSFERRED WITHOUT AN
     EFFECTIVE REGISTRATION THEREOF UNDER SUCH ACT OR PURSUANT TO RULE 144 OR AN
     OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE CORPORATION AND ITS
     COUNSEL THAT SUCH REGISTRATION IS NOT REQUIRED.

          4.3  COMPLIANCE WITH SECURITIES LAWS ON TRANSFER. This Warrant and the
Shares issuable upon exercise this Warrant (and the securities issuable,
directly or indirectly, upon conversion of the Shares, if any) may not be
transferred or assigned in whole or in part without compliance with applicable
federal and state securities laws by the transferor and the transferee
(including, without limitation, the delivery of investment representation
letters and legal opinions reasonably satisfactory to the Company, as reasonably
requested by the Company). The Company shall not require Holder to provide an
opinion of counsel if the transfer is to an affiliate of Holder or if there is
no material question as to the availability of current information as referenced
in Rule 144(c), Holder represents that it has complied with Rule 144(d) and (e)
in reasonable detail, the selling broker represents that it has complied with
Rule 144(f), and the Company is provided with a copy of Holder s notice of
proposed sale.

          4.4  TRANSFER PROCEDURE. Subject to the provisions of Section 4.3
Holder may transfer this Warrant at any time to one of the following entities:
Silicon Valley Bancshares, The Silicon Valley Bank Foundation, or, to any other
affiliate of the Holder (any such transferee is referred to herein as a
"Transferee") by giving the Company notice of such transfer setting forth the
name, address and taxpayer identification number of the Transferee and
surrendering this Warrant to the Company for reissuance to the Transferee.

          4.5  NOTICES. All notices and other communications from the Company to
the Holder, or vice versa, shall be deemed delivered and effective when given
personally or mailed by first-class registered or certified mail, postage
prepaid, at such address as may have been furnished to the Company or the
Holder, as the case may be, in writing by the Company or such holder from time
to time.

          4.6  WAIVER. This Warrant and any term hereof may be changed, waived,
discharged or terminated only by an instrument in writing signed by the party
against which enforcement of such change, waiver, discharge or termination is
sought.

          4.7  ATTORNEYS FEES. In the event of any dispute between the parties
concerning the terms and provisions of this Warrant, the party prevailing in
such dispute shall be entitled to collect from the other party all costs
incurred in such dispute, including reasonable attorneys' fees.

          4.8  GOVERNING LAW. This Warrant shall be governed by and construed in
accordance with the laws of the Commonwealth of Massachusetts, without giving
effect to its principles regarding conflicts of law.


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ATTEST:                                              "COMPANY"

                                                     NovaLink USA Corporation

By: /s/ Dave Rodriguez                               By: /s/ J. Radoff
    ------------------------------------                 -----------------------

Name: David E. Rodriguez                             Name: Jon Radoff
      ----------------------------------                   ---------------------

Title: Assistant Vice President, SVE                 Title: CEO
       ---------------------------------                    ---


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                                   APPENDIX 1

                               NOTICE OF EXERCISE

     1.   The undersigned hereby elects to purchase     shares of the common
stock of NovaLink USA Corporation pursuant to Section 1.1 of the attached
Warrant, and tenders herewith payment of the purchase price of such shares in
full.

     1.   The undersigned hereby elects to convert the attached Warrant into
Shares in the manner specified in Section 1.2 of the attached Warrant. This
conversion is exercised with respect to ________of shares of the common stock of
NovaLink USA Corporation.

     [Strike paragraph that does not apply.]

     2.   Please issue a certificate or certificates representing said shares in
the name of the undersigned or in such other name as is specified below:


                     _____________________________________
                        (Name)


                     _____________________________________

                     _____________________________________
                       (Address)

     3.   The undersigned represents it is acquiring the shares solely for its
own account and not as a nominee for any other party and not with a view toward
the resale or distribution thereof except in compliance with applicable
securities laws.

                                            ___________________________________
                                                      (Signature)

____________________
      (Date)


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                        SCHEDULE 3.1(c) - Capitalization

Outstanding Capital Stock:




Outstanding options, warrants, convertible securities, convertible debentures,
and rights to acquire, subscribe for, and/or purchase any Common Stock and/or
other capital stock of the Company or any securities or debentures convertible
into or exchangeable for Common Stock and/or other capital stock of the Company: