EXHIBIT 4.3
                                                                -----------
Nematron Corporation
April 25, 2003


VIA OVERNIGHT MAIL

Nematron Corporation
5840 Interface Drive
Ann Arbor, Michigan  48103
Attn:  Matthew S. Galvez, President and CEO

                  Re:      Loans by LaSalle Business Credit, LLC

Dear Mr. Galvez:

Reference  is made to that  certain  Amended  and  Restated  Loan  and  Security
Agreement  dated as of June 30,  2000,  as  heretofore  and  hereafter  amended,
amended and restated or otherwise  modified from time to time (the "Agreement"),
by and between  Nematron  Corporation  ("Borrower") and LaSalle Business Credit,
Inc.,  predecessor by merger to LaSalle Business Credit, LLC, a Delaware limited
liability company ("Lender"). Each term set out herein and not otherwise defined
shall have the meaning ascribed to such term in the Agreement.

By our letters to you dated  October 3, 2001 and February 18, 2002,  we notified
you that Borrower is and remains in default (collectively, the Defaults) under
the  Agreement.  The  Defaults  have not been cured or waived.  The terms of the
Agreement  provide  that  Lender  may,  as a result  of any  Event  of  Default,
including  any  Default,  accelerate  the payment of all  Liabilities.  Borrower
acknowledges the existence of each Default.

Lender has requested that Borrower obtain  alternative  financing,  and Borrower
has agreed to use its best efforts to obtain such alternate financing.  However,
Borrower has not yet obtained such alternative financing. Borrower has therefore
requested that Lender not immediately accelerate the payment of the Liabilities,
and that Lender, for the moment,  allow both parties to the Agreement to proceed
under the terms of the  Agreement.  In the event Borrower and each guarantor set
forth herein executes this letter and returns same to Lender,  together with the
fee  described in paragraph (g) below,  on or before May 2, 2003,  Lender hereby
agrees to allow both  parties to proceed  under the terms of the  Agreement  (as
such terms are amended  herein)  until further  notice to Borrower,  provided as
follows:

     (a)      That there occurs no additional Event of Default; and

     (b)      That  there  occurs no  material  adverse  change (as  determined
              by Lender in its sole discretion) in Borrower or in its business;
              and

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     (c)      That  Borrower  shall  use  its  continuing   best  efforts  to
              refinance  all  of  the liabilities with another lender as soon
              as practicable; and

     (d)      That  Borrower  agrees that clause (a) of Section 2 of the
              Agreement is hereby  amended and restated to read in its entirety
              as follows:

                  (a)  during the Original  Term and any Renewal  Term,  absent
                       the existence and  continuation  of an Event of Default,
                       LaSalle  may, in its sole  discretion,  make such
                       revolving  loans and  advances  (the  "Revolving  Loans")
                       to  Borrower as Borrower shall from time to time request,
                       in accordance with the terms of this paragraph 2; and

     (e)      That Borrower  agrees that the definition of "Revolving  Loan
              Commitment"  set forth in Section 1 of the  Agreement is hereby
              amended and restated,  effective as of the date of this letter, to
              read in its entirety as follows:

                   "Loan Commitment" shall mean:

                   (A)  at all  times  prior  to and  including  May 15,  2003,
                        Seven  Hundred Twenty Five Thousand and No/100 Dollars
                        ($725,000.00); and

                   (B)  for the period from May 16, 2003 through and including
                        June 15, 2003:
                        (i) Seven  Hundred Twenty  Five  Thousand  and  No/100
                            Dollars  ($725,000.00)  in the event that (x)
                            Borrower and A-OK shall have  delivered to LaSalle,
                            on or before May 15, 2003, at least three (3)
                            written  proposals (or groups of proposals) from
                            other lenders to refinance  all  Liabilities  at or
                            before the last day of the Original Term (it being
                            understood, for the avoidance of doubt, that any
                            group of proposals which would collectively
                            refinance all Liabilities shall constitute, for
                            these  purposes, one (1) proposal; and (y) LaSalle
                            shall have deemed at least three (3) of such
                            proposals (or groups of proposals)  viable in
                            LaSalle's sole discretion (the occurrence of the
                            conditions  in  clauses  (x)  and (y) is  referenced
                            to herein as a "Timely Proposal Event"); or

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                        (ii)Six Hundred  Twenty Five Thousand and No/100 Dollars
                            ($625,000.00)  in the event a Timely  Proposal Event
                            has not occurred; and

                   (C)  for the period from June 16, 2003, through the end of
                        the Original Term:

                        (i) Seven Hundred Twenty Five Thousand and No/100
                            Dollars ($725,000.00) in the event that (x) a Timely
                            Proposal Event shall have occurred and (y) both (1)
                            Borrower and A-OK shall have delivered to LaSalle,
                            on or before June 15, 2003, at least one (1)
                            written commitment (or group of commitments) from
                            another lender (or lenders) to  refinance all
                            Liabilities at or before the last day of the
                            Original Term, and (2) LaSalle shall have deemed at
                            least one (1) such commitment (or group of
                            commitments) viable in LaSalles sole discretion
                            (the occurrence of the conditions in clauses (y)(1)
                            and (2) is referred to herein as a "Timely
                            Commitment Event"); or

                        (ii)Six Hundred Twenty Five Thousand and No/100  Dollars
                            ($625,000.00)  in the event (x) a Timely Proposal
                            Event has occurred but a Timely Commitment Event has
                            not occurred, or (y) a Timely Commitment Event has
                            occurred but a Timely  Proposal Event has not
                            occurred; or

                        (iii) Five Hundred Twenty Five Thousand and No/100
                            Dollars ($525,000.00) in the event that neither a
                            Timely Commitment Event nor a Timely Proposal Event
                            has occurred.

     (f) That Borrower  agrees that Section 12(a) of the Agreement is hereby
         amended by deleting the date "November 12, 2003" and by inserting the
          date "July 15, 2003" in lieu thereof; and

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     (g) That  Borrower  pays  Lender a fee in the amount of One Thousand and
         No/100  Dollars ($1,000.00) in consideration of Lender's willingness to
         enter into this letter  agreement,  which fees shall be payable, fully
         earned and nonrefundable upon Borrower's acceptance of this letter; and

     (h) That Borrower and each Guarantor agree that all references to LaSalle
         Business  Credit, Inc.  contained in the Agreement and the Other
         Agreements are hereby  deemed to read "LaSalle  Business Credit, LLC".

Borrower  hereby (a) ratifies and affirms its  obligations  under the Agreement;
(b) denies and waives the existence of any defenses  relating to its obligations
under the Agreement;  and (c) waives and releases any claims or causes or action
against  Lender which may now or hereafter be available to it arising out of (i)
the  administration  of  the  Agreement  or  the  Other  Agreements,   (ii)  the
negotiation and execution of this letter,  or (iii) any other matter  pertaining
to the Agreement or the Other Agreements.

Each  of  the  undersigned  guarantors  hereby  (a)  ratifies  and  affirms  its
individual and several obligations under its respective Continuing Unconditional
Guaranty  executed by each guarantor in favor of Lender;  (b)  acknowledges  and
confirms that each Continuing Unconditional Guaranty continues in full force and
effect  notwithstanding  this letter; (c) denies and waives the existence of any
defenses relating to any of such Continuing  Unconditional  Guaranties;  and (d)
waives and releases any claims or causes or action  against Lender which may now
or hereafter be available to any guarantor arising out of (i) the administration
of the Agreement or the Other Agreements, (ii) negotiation and execution of this
letter,  or (iii) any other  matter  pertaining  to the  Agreement  or the Other
Agreements; provided, however, that the failure of any guarantor to execute this
letter shall not release such guarantor or any other guarantor of its respective
obligations under any of the Continuing Unconditional Guaranties.

By this letter  Lender does not waive any Default,  nor any  previous  Events of
Default  about which you have been  notified.  This letter is being written with
Lender reserving all of its rights to exercise any and all of Lender's remedies,
as provided in the Agreement and in all the Other  Agreements,  at such time and
in such  manner as  provided  therein.  Nothing  herein  shall be  construed  or
interpreted as being a waiver of any of Lender's rights or remedies (as provided

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to Lender under the terms of the Other Agreements,  the Uniform  Commercial Code
or otherwise),  by virtue of its  forbearance to date (it being  understood that
Lender has no  obligation  to continue to forbear)  or  extension  with  respect
thereto.
                                      Very truly yours,

                                      LASALLE BUSINESS CREDIT, LLC

                                      By /s/ Dale P. Grzenia
                                      ----------------------
                                      Dale P. Grzenia, First Vice President

Accepted and agreed to this
30th day of April, 2003.

NEMATRON CORPORATION

By /s/ Matthew S. Galvez
------------------------
Its President




Consented and agreed to by
the following guarantors of
the obligations of Nematron Corporation
to LaSalle Business Credit, LLC

A-OK CONTROLS ENGINEERING, INC.     OPTIMATION, INC.

By /s/ David P. Gienapp             By /s/ David P. Gienapp
-----------------------             -----------------------
Its Secretary                       Its Secretary

Date: April 30, 2003                Date: April 30, 2003


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