I believe I understand.  So you've created 3 separate
mail merges that have 3 seperate databases each?  Where
is the data contained, in Access or Excel (in Word 2000
you could use Word's Tables)? If you can find out which
program was used to create all 3 databases that would be
the first start.  The default place Word saves is in "My
Data Sources" folder as an Access File or .mdb extension.

Once you find the 3 databases you'll want to import them
all into one and use that for your mail merge.  I hope I
answered your question, but if I misunderstood then
please let me know.
www.dreamforce.us

Set up a Directory type mailmerge main document with the mergefields in the
cells of a single row table.  Execute that merge against each of the data
sources which will give you three documents, each of which contains a table
with all of the records in it.  Copy and paste the tables from two of the
documents into the third and, if necessary, remove the paragraph mark
between each of the tables so that they join into one.  Then insert a row
and the head of the table into the cells in that row, enter the names of the
mergefields.  Then save that document and use it as your datasource.