A mergefield only outputs the
entire information for the corresponding field in the datasource. Any parsing would have to be done via additional field coding. For numeric data and dates, that's not too hard (the links I've already posted employ such techniques). For text, however, every character in the output would have to be tested. Depending on the data, that could mean 100+ tests per character - hardly a practical proposition.
You can also combine mergefields with other fields to conditionally vary the output. An IF field, for example, might be used to test whether a given mergefield consists of, starts with, or ends with, a particular string and vary the output accordingly. The
'Mailmerge Tips & Tricks' sticky thread (
https://www.msofficeforums.com/mail-...ps-tricks.html) has various examples of such testing.