AMENDMENT TO
                            STOCK PURCHASE AGREEMENT


         This AMENDMENT TO STOCK PURCHASE AGREEMENT ("Amendment") is dated as of
January 12,  1999,  and is entered into by and among Data  Transmission  Network
Corporation,  a Delaware  corporation  ("Buyer"),  and Donald W.  Bowles,  Excel
Interfinancial Corporation,  Charter Financial Holdings, LLC, Steven L. Reynolds
and Douglas Vanderbilt (collectively the "Sellers" and individually a "Seller").

                                    RECITALS:

         A. Buyer and  Sellers are all of the  present  parties to that  certain
Stock Purchase Agreement dated May 27, 1998 (the "Agreement").

         B.  Buyer and  Sellers  desire to  extend by three  months  the term of
certain  earnout  payments to Sellers  under the Agreement as  specifically  set
forth in this Amendment.

         NOW, THEREFORE, in consideration of the mutual covenants and agreements
set forth therein and herein, the parties hereto agree as follows:

         1. Amendments to Agreement. (a) The first sentence of Subsection (b) of
Section  1.02 of the  Agreement  is amended by deleting it in its  entirety  and
inserting the following sentence in its place:

         "Sellers will be paid pro rata, based on their percentage  ownership of
         the Shares, 640% of the amount (the "Excess Amount"),  if any, by which
         the Recurring Revenue (as hereinafter defined) for each of the calendar
         quarters ending June 30, 1998,  September 30, 1998,  December 31, 1998,
         March 31, 1999,  June 30, 1999, and September 30, 1999 exceeds the Base
         Amount (as hereinafter defined)."

               (b) The first  sentence of Subsection  (c) of Section 1.02 of the
Agreement is amended by substituting the date of October 1, 1999 in place of the
date of July 1, 1999 in such sentence.

               (c) The  third  sentence  of  Section  7.02 of the  Agreement  is
amended by deleting it in its entirety and inserting  the following  sentence in
its place:

         "In full consideration for the purchase by Buyer of the Goodwill, Buyer
         shall  pay to Bowles  (i) 160% of the  Excess  Amount  (as  defined  in
         Section  1.02(b))  for each of the  calendar  quarters  ending June 30,
         1998,  September 30, 1998,  December 31, 1998, March 31, 1999, June 30,
         1999, and September 30, 1999 and (ii) 20% of the Non-recurring  Revenue
         (as  defined in Section  1.02(c))  received  by the  Company  after the
         Closing Date and before October 1, 1999."

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         2. Binding  Effect.  This Amendment  shall be binding upon and inure to
the benefit of Buyer and Sellers and their  respective  successors and permitted
assigns.

         3. Superseding.  From and after the date hereof,  all references to the
Agreement shall mean the Agreement, as amended by this Amendment.

         4.  Confirmation.  Except  as  otherwise  expressly  set  forth in this
Amendment,  the  Agreement is hereby  ratified and confirmed and remains in full
force and effect.

         5.  Counterparts.  This  Amendment  may be  executed  in any  number of
counterparts,  all of which taken  together  shall  constitute  one and the same
instrument  and any of the parties  hereto may execute this Amendment by signing
any such counterpart.

         IN WITNESS WHEREOF,  the parties have executed this Amendment as of the
date and year first above written.

                                   DATA  TRANSMISSION  NETWORK
                                   CORPORATION


                                   By: /s/ Charles R. Wood
                                      Charles R. Wood, Sr. Vice President



                                   /s/ Donald W. Bowles
                                   --------------------------
                                   Donald W. Bowles


                                   EXCEL INTERFINANCIAL CORPORATION


                                   By: /s/ Richard Muir
                                        -------------------------------------
                                       Richard Muir, Executive Vice President



                                   CHARTER FINANCIAL HOLDINGS, LLC


                                   By: /s/ John L. O'Donnell
                                        ------------------------------------
                                       John L. O'Donnell, Manager

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                                   /s/ Steven L. Reynolds
                                   ----------------------------------------
                                   Steven L. Reynolds

                                   /s/ Douglas Vanderbilt
                                   ----------------------------------------
                                   Douglas Vanderbilt
                                      
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