<PAGE>

                                                                    EXHIBIT 4.10

THIS WARRANT AND THE SECURITIES ISSUABLE UPON ITS EXERCISE (TOGETHER, THE
"SECURITIES") HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED (THE "ACT"), AND MAY NOT BE TRANSFERRED EXCEPT PURSUANT TO AN EFFECTIVE
REGISTRATION UNDER THE ACT OR IN A TRANSACTION WHICH QUALIFIES AS AN EXEMPT
TRANSACTION UNDER THE ACT AND THE RULES AND REGULATIONS PROMULGATED THEREUNDER.

Date: September 28, 1999

                                 Commerx, Inc.

                   Series B Preferred Stock Purchase Warrant

     Commerx, Inc., a Delaware corporation (the "Company"), hereby certifies
that, for value received, David Franco (the "Holder"), or assigns, is entitled,
subject to the terms set forth below, to purchase from the Company, at any time
and from time to time during the period beginning on the closing of a private
placement of the Company's Series B Preferred Stock and ending on September 28,
2004, an aggregate number of fully paid and non-assessable shares of the
Company's Series B Preferred Stock at the "Purchase Price" (as hereinafter
defined), subject to the provisions of Paragraph 3 hereof, determined by a
fraction, the numerator of which is fifteen percent (.15) multiplied by
$179,179, plus accrued and unpaid interest under the Company's Convertible Note
issued to the holder concurrently with this Warrant, and the denominator of
which is the Purchase Price.  "Purchase Price" shall mean the conversion price
of the Series B Preferred Stock as determined by paragraph 4 of the Convertible
Note.  "Series B Preferred Stock" shall mean, unless the context otherwise
requires, the Series B Preferred Stock issued in accordance with a proposed
amendment to the Company's Certificate of Incorporation, which stock shall have
the rights and preferences substantially as set forth in the Term Sheet attached
hereto and which stock shall be convertible into the Company's Common Stock at
the applicable conversion price as determined by paragraph 4 of the Convertible
Note.  Notwithstanding the foregoing, the Purchase Price and the number and
character of shares issuable under this Warrant are subject to adjustment as set
forth in Paragraph 3.  If the Company consummates an initial public offering of
its common stock prior to exercise of this Warrant, then this Warrant shall be
null and void and the Company shall issue a replacement warrant for the purchase
of Common Stock on equitable terms.  This Warrant and any replacement warrant is
herein called the "Warrant."

     1.  EXERCISE OF WARRANT.  The purchase rights evidenced by this Warrant
shall be exercised by the holder hereof by surrendering this Warrant, with the
form of subscription at the end hereof duly executed by such holder, to the
Company at its office at 350 North LaSalle Street, Suite 1000, Chicago, Illinois
60610, or such other address as the Company may specify by written notice to the
registered holder hereof, accompanied by payment, in cash, by certified or
official bank check or by wire transfer of an amount equal to the Purchase Price
multiplied by the number of shares being purchased pursuant to such exercise of
the Warrant.

         1.1.  Partial Exercise.  This Warrant may be exercised for less than
               ----------------
the full number of shares of Series B Preferred Stock, in which case the number
of shares receivable upon the exercise of this Warrant as a whole, and the sum
payable upon the exercise of this Warrant as a whole, shall be proportionately
reduced. Upon any such partial exercise, the Company at its expense will
forthwith issue to the holder hereof a new Warrant or Warrants of
<PAGE>

like tenor calling for the number of shares of Series B Preferred Stock as to
which rights have not been exercised, such Warrant or Warrants to be issued in
the name of the holder hereof or his nominee (upon payment by such holder of any
applicable transfer taxes).

          1.2. Net Issue Exercise.
               ------------------

               (1)  In lieu of exercising this Warrant, holder may elect to
receive shares equal to the value of this Warrant (or the portion thereof being
canceled) by surrender of this Warrant at the principal office of the Company
together with notice of such election in which event the Company shall issue to
holder that number of shares of the Company's Series B Preferred Stock computed
using the following formula:

                                   X = Y(A-B)
                                       ------
                                         A

Where

          X.   the number of shares of Series B Preferred Stock to be issued to
               Holder.

          Y.   the number of shares of Series B Preferred Stock purchasable
               under this Warrant.

          A.   the fair market value of one share of the Company's Series B
               Preferred Stock.

          B.   the Purchase Price (as adjusted to the date of such
               calculations).

          (2)  For purposes of this Section, the fair market value of one share
of the Company's Series B Preferred Stock shall be the applicable conversion
price of the Series B Preferred Stock.

     2.   DELIVERY OF STOCK CERTIFICATES ON EXERCISE.  As soon as practicable
after the exercise of this Warrant and payment of the Purchase Price, and in any
event within ten (10) days thereafter, the Company, at its expense, will cause
to be issued in the name of and delivered to the holder hereof a certificate or
certificates for the number of fully paid and non-assessable shares or other
securities or property to which such holder shall be entitled upon such
exercise, plus cash in lieu of any fractional share to which such holder would
otherwise be entitled.  The Company agrees that the shares so purchased shall be
deemed to be issued to the holder hereof as the record owner of such shares as
of the close of business on the date on which this Warrant shall have been
surrendered and payment made for such shares as aforesaid.

     3.   ANTI-DILUTION PROVISIONS AND OTHER ADJUSTMENTS.  In order to prevent
dilution of the right granted hereunder, the Purchase Price shall be subject to
adjustment from time to time in accordance with the provisions of the Company's
Series B Preferred Stock.

     If any event occurs as to which, in the opinion of the Board of Directors
of the Company, the provisions of the Company's Series B Preferred Stock
relating to anti-dilution and other adjustments are not strictly applicable or
if strictly applicable would not fairly protect the rights
<PAGE>

of the holder of this Warrant in accordance with the essential intent and
principles of such provisions, then the Board of Directors shall make an
adjustment in the application of such provisions, in accordance with such
essential intent and principles, so as to protect such rights as aforesaid.

     4.   NO DILUTION OR IMPAIRMENT.  The Company will not, by amendment of its
charter or through reorganization, consolidation, merger, dissolution, sale of
assets or any other voluntary action, avoid or seek to avoid the observance or
performance of any of the terms of this Warrant, but will at all times in good
faith assist in the carrying out of all such terms and in the taking of all such
action as may be necessary or appropriate in order to protect the rights of the
holder hereof against dilution or other impairment.  The Company shall at all
times take all such action as may be necessary or appropriate in order that the
Company may validly and legally issue fully paid and non-assessable stock upon
the exercise of this Warrant.

     5.   RESERVATION OF STOCK ISSUABLE ON EXERCISE OF WARRANTS.  The Company
shall at all times reserve and keep available out of its authorized but unissued
stock, solely for the issuance and delivery upon the exercise of this Warrant
and other similar Warrants, such number of its duly authorized shares of Series
B Preferred Stock as from time to time shall be issuable upon the exercise of
this Warrant and all other similar Warrants at the time outstanding.  All of the
shares of Series B Preferred Stock issuable upon exercise of this Warrant, when
issued and delivered in accordance with the terms hereof, will be duly
authorized, validly issued, fully-paid and non-assessable.

     6.   REPLACEMENT OF WARRANT.  Upon 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) upon delivery of an
indemnity agreement (with surety if reasonably required) in an amount reasonably
satisfactory to it, or (in the case of mutilation) upon surrender and
cancellation thereof, the Company will issue, in lieu thereof, a new Warrant of
like tenor.

     7.   REMEDIES.  The Company stipulates that the remedies at law of the
holder of this Warrant in the event of any default by the Company in the
performance of or compliance with any of the terms of this Warrant are not and
will not be adequate, and that the same may be specifically enforced.

     8.   REGISTRATION RIGHTS.  The shares of Series B Preferred Stock issuable
upon exercise of this Warrant and securities issued upon conversion of such
stock are subject to the registration rights granted to Series B Preferred
Stockholders.

     9.   NEGOTIABILITY.  This Warrant is issued upon the following terms, to
all of which each taker or owner hereof consents and agrees:

          (a)  Absent an effective registration statement under the Securities
Act of 1933, as amended (the "Act"), covering the disposition of this Warrant or
the shares of Series B Preferred Stock issued or issuable upon exercise hereof,
the holder will not sell or transfer any or all of such Warrant or shares, as
the case may be, without first providing the Company with an opinion of counsel
(which may be counsel for the Company) to the effect that such sale or
<PAGE>

transfer will be exempt from the registration and prospectus delivery
requirements of the Act. Each certificate representing shares of Series B
Preferred Stock issued pursuant to this Warrant shall bear a legend in
substantially the following form on the face thereof:

          THESE SECURITIES HAVE NOT BEEN REGISTERED
          UNDER THE SECURITIES ACT OF 1933 OR APPLICABLE
          STATE SECURITIES LAWS AND MAY BE TRANSFERRED
          OR RESOLD ONLY IN COMPLIANCE WITH SUCH
          SECURITIES LAWS.

Any certificate representing securities issued at any time in exchange or
substitution for any certificate bearing such legend (except a certificate
issued upon completion of a distribution under a registration statement covering
the securities represented) shall also bear such legend unless, in the opinion
of counsel to the Company, the securities represented thereby may be transferred
as contemplated by such holder without violation of the registration
requirements of the Act.

          (b)  Any person in possession of this Warrant properly endorsed is
authorized to represent itself as absolute owner hereof and is granted power to
transfer absolute title hereto by endorsement and delivery hereof to a bona fide
purchaser hereof for value; each prior taker or owner waives and renounces all
of its equities or rights in this Warrant in favor of every such bona fide
purchaser, and every such, bona fide purchaser shall acquire title hereto and to
all rights represented hereby.

          (c)  Until this Warrant is transferred on the books of the Company,
the Company may treat the registered holder of this Warrant as the absolute
owner hereof for all purposes without being affected by any notice to the
contrary.

          (d)  Prior to the exercise of this Warrant, the holder hereof shall
not be entitled to any rights of a shareholder of the Company with respect to
shares for which this Warrant shall be exercisable, including, without
limitation, the right to vote, to receive dividends or other distributions or to
exercise any preemptive rights, and shall not be entitled to receive any notice
of any proceedings of the Company, except as provided herein.

          (e)  The Company shall not be required to pay any Federal or state
transfer tax or charge that may be payable in respect of any transfer involved
in the transfer or delivery of this Warrant or the issuance or conversion or
delivery of certificates for Series B Preferred Stock in a name other than that
of the registered holder of this Warrant or to issue or deliver any certificates
for Series B Preferred Stock upon the exercise of this Warrant until any and all
such taxes and charges shall have been paid by the holder of this Warrant or
until it has been established to the Company's satisfaction that no such tax or
charge is due.

     10.  REPRESENTATIONS AND WARRANTIES OF THE COMPANY.  This Warrant is issued
and delivered by the Company on the basis of the following:

          (a)  Authorization and Delivery.  This Warrant has been duly
               --------------------------
authorized and executed by the Company and when delivered will be the valid and
binding obligation of the Company enforceable in accordance with its terms;
<PAGE>

          (b)  Rights and Privileges.  The Company shall, as soon as
               ---------------------
practicable, use its best efforts to amend its Certificate of Incorporation to
authorize the issuance of a class of Series B Preferred Stock having the rights,
preferences, privileges and restrictions, substantially as set forth in the
attached Term Sheet; and

          (c)  Warrant Shares.  The shares of Series B Preferred Stock to be
               --------------
issued pursuant to this Warrant will be, upon proper exercise of this Warrant,
duly authorized and reserved for issuance by the Company and, when issued and
paid for in accordance with the terms hereof, will be validly issued, fully paid
and nonassessable;

          (d)  No Inconsistency.  The execution and delivery of this Warrant are
               ----------------
not, and the issuance of the shares of Series B Preferred Stock upon exercise of
this Warrant in accordance with the terms hereof will not be, inconsistent with
the Company's Certificate of Incorporation or by-laws, will not contravene any
law, governmental rule or regulation, judgment or order applicable to the
Company, and do not and will not contravene any provision of, or constitute a
default under, any indenture, mortgage, contract or other instrument of which
the Company is a party or by which it is bound or require the consent or
approval of any other person.

     11.  REPRESENTATIONS AND WARRANTIES OF HOLDER.

          (a)  The holder hereby represents and warrants to the Company that he
has substantial knowledge, skill and experience in making investment decisions
of the type represented by this Warrant and the shares issuable upon exercise of
this Warrant, that he is capable of evaluating the risk of its investment in
this Warrant and the shares issuable upon exercise of this Warrant and is able
to bear the economic risk of such investment, including the risk of losing the
entire investment, that it is acquiring this Warrant and the shares issuable
upon exercise of this Warrant for his own account, and that this Warrant and the
shares issuable upon exercise of this Warrant are being acquired by him for
investment and not with a present view to any distribution thereof in violation
of applicable securities law.  If the holder should in the future decide to
dispose of any of this Warrant and the shares issuable upon exercise of this
Warrant, it is understood that it may so do only in compliance with the Act and
applicable state securities laws.  The holder represents and warrants that he is
an "Accredited Investor" as defined in Rule 501(a) under the Act.

          (b)  The holder understands that (i) this Warrant and the shares
issuable upon exercise of this Warrant have not been registered under the Act by
reason of their issuance in a transaction exempt from the registration
requirements of the Act, (ii) this Warrant and the shares issuable upon exercise
of this Warrant must be held indefinitely unless a subsequent disposition
thereof is registered under the Act and applicable state securities laws or is
exempt from such registration (and, upon request, evidence satisfactory to the
Company is provided by such holder of the availability of such exemptions,
including, upon request, the delivery to the Company of opinions of counsel to
such holder, which opinions and counsel are satisfactory to the Company), and
(iii) this Warrant and the shares issuable upon exercise of this Warrant may
bear a legend to such effect.
<PAGE>

     12.  SUBDIVISION OF RIGHTS.  This Warrant (as well as any new warrants
issued pursuant to the provisions of this paragraph) is exchangeable, upon the
surrender hereof by the holder hereof, at the principal office of the Company
for any number of new warrants of like tenor and date representing in the
aggregate the right to subscribe for and purchase the number of shares of Series
B Preferred Stock of the Company that may be subscribed for and purchased
hereunder.

     13.  MAILING OF NOTICES.  All notices and other communications from the
Company to the holder of this Warrant shall be mailed by first-class certified
mail, postage prepaid, to the address furnished to the Company in writing by the
last holder of this Warrant who shall have furnished an address to the Company
in writing.

     14.  HEADINGS.  The headings in this War-rant are for purposes of reference
only, and shall not limit or otherwise affect the meaning hereof.

     15.  CHANGE, WAIVER.  Neither this Warrant nor any term hereof may be
changed, waived, discharged or terminated orally but only by an instrument in
writing signed by the party against which enforcement of the change, waiver,
discharge or termination is sought.

     16.  GOVERNING LAW.  This Warrant shall be construed and enforced in
accordance with the laws of the State of Delaware.
<PAGE>

     IN WITNESS WHEREOF, the Company, by the undersigned thereunto duly
authorized, has duly executed this Warrant as of the date first written above.

                              COMMERX, INC.


                              By:  /s/ Tim Stojka
                                   -------------------------------
                              Name:  Tim Stojka
                              Title: Chief Executive Officer


                              ACCEPTED AS OF THE DATE HEREOF:


                              /s/  David Franco
                              ------------------------------------
                              Name:  David Franco
<PAGE>

                  [To be signed only upon exercise of Warrant]


To__________________:

     The undersigned, the holder of the within Warrant, hereby irrevocably
elects to exercise the purchase right represented by such Warrant for, and to
purchase thereunder, ________ shares of Series B Preferred Stock of and herewith
makes payment of $_______ therefor, and requests that the certificates for such
shares be issued in the name of, and be delivered to _____________, whose
address is ______________.

Dated:________________


                              __________________________________________________

                              By________________________________________________

                              (Signature must conform in all respects to name of
                              Holder as specified on the face of the Warrant)

                              Address:

                              __________________________________________________

                              __________________________________________________
<PAGE>

                  [To be signed only upon transfer of Warrant]

          FOR VALUE RECEIVED, the undersigned hereby sells, assigns and
transfers unto _____________ the right represented by the within Warrant to
purchase the _____ shares of the Series B Preferred Stock of __________________
to which the within Warrant relates, and appoints ____________ attorney to
transfer said right on the books of __________________________ with full power
of substitution in the premises.

Dated:________________

                              __________________________________________________

                              By________________________________________________

                              (Signature must conform in all respects to name of
                              Holder as specified on the face of the Warrant)

                              Address:

                              __________________________________________________

                              __________________________________________________