Using dates during mail merge

Can anybody help please?

Using Word 2000 (9.0.2760) we are in the process of setting up a mail merge
using a standard letter for the main document. The data source comprises in
each record, name, address and other data fields. Data will accumulate slowly
in each record, but we need to carry out mail merges at frequent intervals.

Letters generated during each mail merge must be dated with the current date,
but each date must be retained in the relevant data source records for
generating ‘directories/catalogues’ at a later time (using separate mail
merges) for review. It would also be beneficial for each mail merge to
produce only those letters with the current date, ie. not all record are
merged.

How can this be done, please?

Many thanks in anticipation.