<PAGE>

                                 Exhibit 10.21

1. Proposed Services

   1.1.  Helix will act as the Company's  exclusive  mergers & acquisitions  and
         principal  financial  advisor and will assist the Company in analyzing,
         structuring, negotiating, and effecting the Transactions, including the
         Proposed  Transactions  (as  described in section 1.3) on the terms and
         conditions of this Agreement, below. In parallel with services relating
         to the  Proposed  Transactions,  Helix will assist and consult with the
         Company on  strategic  financial  and  operational  issues and tactical
         implementation of concepts relating to the growth of the Company.

   1.2.  Helix will assign its  Managing  Partner,  Yoav Stern,  to serve on the
         Company's board of directors as Co-Chairman and member of the executive
         committee of the board.  Mr. Stern will devote a substantial  amount of
         his time, as needed from time to time, to participate in meetings, lead
         strategic  planning  sessions,  initiate  and  help in  recruiting  key
         personnel and advise management on operational  issues in growth and/or
         turn around situations. Mr. Stern will not receive any fees in addition
         to the compensation described in section 2.3 herein.

   1.3.  Proposed Transaction(s):

         1.3.1. M&A Transaction:  As used herein, the term  "Transaction"  shall
                mean any  transaction or series of  transactions  other than the
                purchase  or  sale  of  assets  in the  ordinary  course  of the
                Company's business, whereby, directly or indirectly, the Company
                or any of its  businesses,  assets or  properties  acquires,  is
                acquired  by or is  merged  with  another  entity,  or any other
                similar business  transaction or arrangement between the Company
                and a third  party,  including  without  limitation,  a  merger,
                combination  or  consolidation,  regardless of the accounting or
                tax treatment of such transaction.

         1.3.2. Other Transactions: As used herein, the term "Transaction" shall
                also mean any transaction or series of  transactions  other than
                senior debt  financing  transactions  arranged by the  Company's
                management in the ordinary course of business, whereby, directly
                or  indirectly,  the Company or any of its  businesses  receives
                additional capital,  debt financing or markets additional equity
                other  than   through  a  public   offering.   With   regard  to
                transactions  described in this  section  1.3.2,  the  Company's
                obligation  to  retain  Helix  is  subject  and  subordinate  to
                existing  agreements with  investment  banking firms relating to
                private debt or equity financing.  Moreover, the Company retains
                the right to engage an  investment  banking firm to assist it in
                arranging any such  Transaction,  provided that the Company will
                notify Helix in


                                       -2-

<PAGE>

<PAGE>

                writing 60 days in advance regarding a proposed  engagement with
                any investment  banking firm. No fee will be payable to Helix as
                per section 2.3 with regards to any Transaction  arranged by any
                such investment banking firm.

   1.4. Other  Activities:  Helix  will  undertake  certain  activities  on  the
        Company's behalf, including, if appropriate, the following:

        1.4.1. Assisting the Company in its determination of appropriate  values
               to be realized in Transactions;

        1.4.2. Advising  the  Company  in the  negotiations  as to the  form and
               structure of Transactions;

        1.4.3. Advising  and  assisting  the  Company's   management  in  making
               presentations   to  the  Company's   Board  of  Directors   about
               Transactions;

        1.4.4. In addition to advising on any Transactions, rendering such other
               financial advisory and merchant banking services as may from time
               to time be agreed in writing between Helix and the Company.

2. Further Agreement Terms

   2.1. Transaction  Timing. A Transaction shall be deemed to have occurred when
        Consideration  Paid  for a  Transaction,  having  been  received  by the
        Company  or the  Company's  shareholders,  or in the  event of a merger,
        acquisition,  purchase by the Company,  Consideration Paid has been sent
        to the receiving party,  provided that if,  Consideration  Paid shall be
        paid in  installments,  the full amount will be  construed  to have been
        received  on the  receipt  of the first  installment  exchanged  between
        parties to a Transaction.

   2.2. Limitation and Exclusivity. To the extent that this agreement created an
        exclusive  relationship with Helix in cases of Transactions described in
        section  1.3.2,  and in all cases of  Transactions  described in section
        1.3.1, the Company agrees that as of the date hereof, Helix shall be the
        exclusive  advisor to the Company  and the Company  shall not enter into
        any  agreement  relating  to a  Transaction  during  the  term  of  this
        Agreement without the participation of Helix. If the Company consummates
        a Transaction  during the term of this Agreement (or for a period of one
        year thereafter as described below) without Helix's  participation,  the
        Company  agrees  that  it,  and  its   successors  and  assigns,   shall
        nevertheless  be  obligated to provide or cause to be provided to Helix,
        the compensation provided herein in paragraph 2.3.



                                       -3-

<PAGE>

<PAGE>

  
 2.3.   Compensation.  The  Company  will  compensate  Helix  in the  form  of a
        retainer,  success fees and reimbursement of its reasonable  expenses as
        described below. Fees will be paid directly to Helix Capital LLC., or to
        another entity as assigned from time to time by Helix.

        2.3.1. Retainer:  The Company  will pay Helix a monthly  retainer in the
               amount  of  $25,000  for  a  minimum  period  of  18  months  and
               thereafter for the length of this  Agreement (see  Termination in
               paragraph 2.8)

        2.3.2. Consideration   Paid:   For  the   purpose  of  this   Agreement,
               Consideration Paid is defined as:

               2.3.2.1. In the event of a sale by the  Company  of newly  issued
                        securities, the amount of cash invested in the Company;

               2.3.2.2. In the  event of a sale,  merger or  acquisition  of the
                        Company or the Company's assets,  the cash consideration
                        plus the market  value of non-cash  consideration,  plus
                        the   amount   of  debt  and  other   interest   bearing
                        obligations  assumed,  refinanced  by the  acquiror,  or
                        retired,   or   defeased,   in   connection   with   the
                        Transaction;

               2.3.2.3. In  the  event  of a  purchase,  merger  or  acquisition
                        Transaction  by the Company,  the purchase  price of the
                        equity  paid plus the amount of debt and other  interest
                        bearing   Obligations   assumed  or  refinanced  by  the
                        Company,  less any cash  retained  by the  Company  upon
                        successful completion of the Transaction.

               2.3.2.4. The  fair  market  value of any  non-cash  consideration
                        delivered in a Transaction will be the value agreed upon
                        by the Company and Helix  prior to the  consummation  of
                        the Transaction.

        2.3.3. Success fees:

               2.3.3.1. For an M&A  Transaction  as defined in section 1.3.1 the
                        Company  shall pay Helix a success  fee upon  closing of
                        each  Transaction.  Success fees for any  Transaction as
                        defined  above,  will be determined by mutual consent by
                        Helix and the Company based on market  conditions and on
                        a per Transaction basis, but in any case will be no less
                        than 2% of the

                                       -4-

<PAGE>

<PAGE>

                        Consideration  Paid  transferred to or transferred  from
                        the Company or the Company's shareholders.  Success fees
                        shall be due and  payable  if the  Company  completes  a
                        Proposed  Transaction  during the term of this Agreement
                        and within one year of the termination of this Agreement
                        with a party  introduced  by or that was in contact with
                        Helix  within the term of this  Agreement.  This success
                        fee  will  be  paid  in  cash,  or in  other  negotiable
                        securities  and financial  instruments  as  specifically
                        agreed in writing by Helix and the Company.

               2.3.3.2. For any other  Transaction  as defined in section 1.3.2,
                        the  Company  and Helix  will reach and  agreement  on a
                        success fee for each  specific  Transaction  if and when
                        the Company  instructs Helix to proceed with preparation
                        for a specific Transaction.

        2.3.4. Expenses: The Company shall reimburse Helix, upon Helix's request
               and   regardless   of  whether   the  Company   consummates   any
               Transactions,  for  its  reasonable  and  actual  out  of  pocket
               expenses incurred by it in connection with this Agreement.  In on
               event,  however,  shall  the  Company  be  liable  to  Helix  for
               out-of-pocket expenses in excess of $10,000 per month without the
               prior approval of Kellstrom.

        2.3.5  Life  Insurance.  The Company  shall  obtain and  maintain a life
               insurance  policy  on the  life of Mr.  Stern  in the  amount  of
               $3,000,000 with a variable annuity feature mutually acceptable to
               Mr.  Stern and the  Company.  The Company will pay the premium on
               such policy for the entire  period  commencing  on the  effective
               date of this  agreement and ending on the seventh  anniversary of
               the date hereof (the "Policy Period"). Until January 1, 1999, the
               Company  shall  own,  and shall have the right to  designate  the
               beneficiary  under, such insurance  policy.  Mr. Stern shall have
               the option of causing the Company to transfer the   ownership  of
               the  policy  (and  the  right  to   designate   the   beneficiary
               thereunder) to Mr. Stern at no cost to Mr. Stern after January 1,
               1999  (but  the  Company  will   continue   to  pay  the  premium
               on such policy for the entire Policy  Period).  If Mr. Stern does
               not exercise his option to transfer ownership of the policy, upon
               the termination of the Policy Period,  the Company shall transfer
               the  policy  to  Mr . Stern at no cost to Mr. Stern. In the event
               that  this  agreement is terminated (other than as a result  of a
               breach  by Helex  of  the  terms of this agreement) prior to that
               time,  the  Company  will  transfer  ownership  of  the policy to
               Mr. Stern and pay Mr. Stern a  lump  sum  payment  equal  to  the
               unpaid premium remaining through the end of  the  Policy  Period.
               Such lump sum  payment  shall  include  an  amount  sufficient to
               compensate Mr. Stern for any Federal, state or local income taxes
               associated with the receipt of such payment.

   2.4. Information  & Reliance:  In  connection  with Helix's  engagement,  the
        Company will furnish Helix with all  information  concerning the Company
        which Helix and the Company deem appropriate and will provide Helix with
        access to the Company's officers, directors, accountants and counsel. It
        is understood  that Helix will rely on the accuracy and  completeness of
        such information  supplied by the Company,  its officers and agents,  or
        available  from  generally   recognized  public  sources,   without  any
        independent investigation or verification thereof.

   2.5. Confidentiality.   Any  advice,  data,  materials,   contacts  or  other
        information  provided by Helix,  its affiliates or  subsidiaries  to the
        Company under this Agreement, including the existence of this Agreement,
        shall  not  be  disclosed  to  third  parties   other  than   attorneys,
        representatives and affiliates controlled by the Company,  except to the
        extent such disclosure is in the opinion of counsel,  required by law or
        legal  process,  without  prior  written  approval  by  Helix,  it being
        understood  that a copy  of  this  Agreement  must  be  filed  with  the
        Securities  and  Exchange  Commission  and its  terms  be  described  in
        Company's public filings.  All non-public  information given to Helix by
        the Company will, likewise, be treated by Helix as confidential.


                                       -5-

<PAGE>

<PAGE>

   2.6. Indemnification. The Company agrees to indemnify and hold Helix harmless
        from and against any and all losses, claims, damages and liabilities (or
        actions including security holder actions in respect thereof) related to
        or arising out of Helix's engagement hereunder or its role in connection
        herewith,   and  will  reimburse  Helix  for  all  reasonable   expenses
        (including reasonable counsel fees and expenses) as they are incurred by
        Helix in connection with  investigating,  preparing for or defending any
        such  action or claim,  whether  or not in  connection  with  pending or
        threatened  litigation  in which  Helix is a party  and  whether  or not
        initiated by or on behalf of the Company. The Company will not, however,
        be responsible for any claims, liabilities,  losses, damages or expenses
        which have resulted from the bad faith or gross negligence of Helix. The
        Company  also  agrees  that Helix  shall not have any  liability  to the
        Company  for  or in  connection  with  Helix's  engagement,  except  for
        liability for losses, claims, damages,  liabilities or expenses incurred
        by the Company  that result  from the bad faith or gross  negligence  of
        Helix.

        2.6.1. In the event that the foregoing  indemnity is  unavailable,  then
               the Company shall  contribute to amounts paid or payable by Helix
               in respect of its losses, claims, damages and liabilities:

               2.6.1.1. in  such  proportion  as   appropriately   reflects  the
                        relative  benefits received by, the Company and Helix in
                        connection  with the  matters as to which  such  losses,
                        claims, damages or liabilities relate, or

               2.6.1.2. if (but only if) the allocation  provided for in 2.6.1.1
                        is  for  any  reason  held  to  unenforceable,  in  such
                        proportion  as is  appropriate  to reflect  not only the
                        relative  benefits  referred  to in 2.6.1.1 but also the
                        relative fault of the Company and Helix,  as well as any
                        other relevant equitable considerations;

               2.6.1.3. provided,  however, that in no event shall the amount to
                        be  contributed  by Helix  exceed  the amount of the fee
                        actually  received by Helix.  The foregoing  shall be in
                        addition to any rights that Helix may have at common law
                        or otherwise and shall extend upon the same terms to and
                        inure to the  benefit  of Helix and its  affiliates  and
                        their respective directors,  officers, employees, agents
                        or controlling persons of Helix.

               2.6.1.4. The Company agrees that,  without  Helix's prior written
                        consent,  it will not settle,  compromise  or consent to
                        the entry of any  judgment in any pending or  threatened
                        claim, action, or proceeding in respect

                                       -6-

<PAGE>

<PAGE>


                        of which  indemnification  could  be  sought  under  the
                        indemnification provisions of this Agreement (whether or
                        not Helix or any other  party is an actual or  potential
                        party to such claim, action or proceeding),  unless such
                        settlement,    compromise   or   consent   includes   an
                        unconditional release of each indemnified party from all
                        liability   arising  out  of  such   claim,   action  or
                        proceeding.

   2.7.  Limited Commitment.  It is understood that Helix makes no commitment to
         raise  capital  and/ or effect  any of the  Proposed  Transactions.  In
         addition,  the  Company  has the right not to accept  any or all offers
         with respect to the Proposed Transactions.

   2.8.  Term and  termination.  This Agreement shall have an initial term of 18
         months  from  January  1,  1997,  and  will  be  renewed  automatically
         thereafter  for  additional  12  month-terms  every 12  months,  unless
         terminated by written  notice at least 90 days prior to the last day of
         the   initial   term  or  any   extensions   thereof,   by  any  party.
         Notwithstanding  the foregoing,  the provisions of paragraphs 2.3, 2.5,
         2.6 and 2.8 will survive any termination.

   2.9.  Governing  Law.  This  Agreement  shall be governed by and construed in
         accordance  with the laws of the State of Florida and the federal  laws
         of the United States of America applicable therein.  Any controversy or
         claim  arising out of or relating  to this  letter  agreement  shall be
         settled by  arbitration  in  accordance  with the rules of the American
         Arbitration  Association,   and  judgment  upon  an  award  arising  in
         connection   therewith  may  be  entered  in  any  court  of  competent
         jurisdiction.

   2.10. Survival.  In the event that any  provision  herein is determined to be
         unenforceable  under the current law at the time of  execution  of this
         letter Agreement,  or unenforceable under a law that may supersede that
         law in place at the time of  execution,  all other  provisions  and the
         intent of this Agreement shall survive such findings.

   2.11. Independent Contractor.  The Company acknowledges and agrees that Helix
         has been retained solely as a M&A and financial advisor to the Company.
         In such capacity, Helix shall act as an independent contractor, and any
         duties arising out of its engagement  pursuant to this Agreement  shall
         be owed solely to the Company.

   2.12. Waiver of Rights.  No  provision  of this  Agreement  may be  modified,
         waived or discharged  unless such waiver,  modification or discharge is
         agreed to in writing by the party against whom the same is sought to be
         enforced and no failure by either party to enforce any of its rights

                                       -7-

<PAGE>

<PAGE>

         hereunder shall, except as aforesaid,  be deemed to be a waiver of such
         right.  No waiver by either  party  hereto at any time of any breach by
         the other party hereto of, or  compliance  with,  any provision of this
         Agreement  to be  performed by such other party shall be deemed to be a
         waiver of a similar or dissimilar  provision  hereof at the same or any
         prior or subsequent time.

   2.13. Notices.  Any  notice  required  or  permitted  to be given  under this
         Agreement  shall be in writing and shall be properly given if delivered
         personally,  mailed prepaid registered mail, overnight courier, or sent
         by  telecopy  (as long as the  telecopy  is  followed  by a hard  copy)
         addressed as follows:

         In the case of Helix:
         Alex Hoag
         Helix Capital L.L.C.
         98 Battery Street
         Suite 600
         San Francisco, CA  94104
         Tel:  (415) 956-9950 Fax:  (415) 956-9951

         In the case of Kellstrom:
         John Gleason
         Chief Financial Officer
         14000 NW 4th St.
         Sunrise, Florida 33325
         Tel:  (954) 845-0427 Fax:  (954) 845-0428

         or to such other address as the parties shall from time to time specify
         by notice given in  accordance  herewith.  Any notice so given shall be
         conclusively  deemed to have been given or made on the day of delivery,
         if delivered,  if mailed by registered mail, upon the date shown on the
         postal  return  receipt as the date upon which the envelope  containing
         such notice was  actually  received by the  addressee,  if delivered by
         overnight  courier,  two (2) days  after  deposit  with  the  overnight
         courier, and if by telecopy,  upon transmission thereof, as long as the
         telecopy is followed by delivery of a hard copy.

   2.14. Entire Agreement. This mutually signed Agreement, attached Exhibits and
         any properly  executed and signed  Amendments,  constitutes  the entire
         agreement  between the parties with respect to the  engagement of Helix
         contemplated  hereby and cancels and supersedes all prior  undertakings
         and  agreements  between  the  parties  with  respect  thereto  and  no
         agreements or representations,  oral or otherwise,  express or implied,
         with  respect to the  subject  matter  hereof  have been made by either
         party which are not expressly set forth in this Agreement.


                                       -8-

<PAGE>

<PAGE>


3. Miscellaneous.  Each of the parties  represents that it is duly authorized to
   execute  this  Agreement.  This  Agreement  may be  executed in any number of
   counterparts,  each of which  shall be  deemed to be an  original  and all of
   which together shall be deemed to be the same agreement.

   If you are in  agreement  with the  foregoing,  please  execute a copy in the
   space provided below and return it to Helix Capital Corporation, L.L.C.

Regards,

Helix Capital Corporation, LLC

For Helix Capital Corporation, LLC

By: /s/
    --------------------------------------
Name:    Alexander W. Hoag
Title:   Vice President, Partner

Accepted this 24 of December, 1996

For Kellstrom Industries Inc.

By: /s/
    ---------------------------------------
Name:    John Gleason
Title:   Chief Financial Officer

                                       -9-

<PAGE>

<PAGE>


Qualifications.

Alexander  Hoag is a Partner and Vice  President of Helix  Capital  Corporation,
L.L.C.  He  brings   extensive   experience  in  technology   company  Merger  &
Acquisitions,  Marketing,  Operations  and Research & Development in some of the
preeminent  success  stories of the software  industry.  Mr. Hoag will lead this
effort and will be the primary  contact  and  manager of Helix's  efforts on The
Company's behalf.

Until  recently  he served as  Executive  Vice  President,  Products,  and Chief
Technology Officer of SoftKey  International  Inc., a Massachusetts  based $350M
consumer  software  company that  culminated the  successful  turn around effort
begun at WordStar  International  in 1990.  Previous  experience at Quark,  Inc.
(Director of Marketing),  Broderbund Software Inc. (Publisher,  NASDAQ:BROD) and
Blyth Software, Inc. (Vice President,  Special Markets,  NASDAQ:BLY) represent a
string of successful  product,  divisional and company turnarounds where leading
competitive positions were forged from undercapitalized or competitively laggard
entities.  In each case, Mr. Hoag was instrumental in reorganizing the strategic
focus, building management,  marketing and development teams, and establishing a
series of  defensible  product  and company  niches that have won  significantly
improved  shareholder returns as well as industry  recognition for distinguished
achievement.

Mr.  Hoag  holds a Masters of  International  Business  Administration  from The
Monterey Institute (Monterey, California) and a BA in Political Science from the
University of California, San Diego.

OGEN PERRY is a Partner  and  Director  of Helix  Capital.  He brings  extensive
experience in M&A and strategic planning.

Mr.  Perry  joined  Helix from  Intel  Corporation  where he served as  manager,
Corporate  Business  Development.  At Intel,  he spearheaded  several  strategic
investments in emerging technology companies including  networking,  compression
and database software.

Prior to Intel, Mr. Perry was an Engagement Manager with McKinsey & Co., leading
consultant and client teams in the development business strategies.

Until  1987,  Mr.  Perry  was  New  Business   Development  Manager  for  Matrix
Instruments, Inc. Mr. Perry's efforts to create a VAR program and to promote the
adoption of the company's high level graphics language contributed to a doubling
of division sales.

Mr.  Perry holds and MBA in finance  from the Wharton  School as well as an M.E.
and a B.Sc. in Computer Engineering from Rensselaer Polytechnic Institute.

                                      -10-




<PAGE>