Longer term it will probably be better to set up one letter (i.e. Mailmerge
main document) for each term, and use the Mailmerge Recipients dialog
(depends on the version of Word) to select the applicable records. Within
that dialog, select the little drop-down at the top of the TermYear field
and select what you need (what does the field actually contain? Does it
contain a year and a term, or just a term?). You may need to select the
Advanced... option there which leads to another dialog box where you can set
up the criteria.

Once you have made the selection, save the mail merge main document, close
it, and re-open it to ensure that your selections have not been lost or
altered (Word does not have a particularly good track record in this area).
Then test the merge (e.g. by merging to a new document).

Peter Jamieson