Hi Roger,
Without details of your tables/relationships, it's difficult to be exact.
However, I expect that all you'd probably need is an additional field in one
(or maybe more) table(s) to hold the AccountNumber, which you can then use
in your queries to separate the records as desired. You can fill this field
for each database using an Update query; and then merge the tables via a
series of Append queries.
If you've got autonumber fields used as primary keys, which are used as
foreign keys in relationships, it becomes somewhat more complicated, as the
primary key will change when you do the append, but the foreign keys will
not. You will need to copy the existing autonumber field to a new field
before doing the append, and later use this field to link with the related
tables in update queries to change the foreign keys to the correct new
values.
HTH,
Rob