What you're asking for isn't possible - VBA cannot create new field functions. If the field data are purely numeric, you could use Word's INT and/or MOD math functions to truncate them. Beyond that, you'd have to edit the data post-merge, bearing in mind that there will be no mergefields in the output and any bookmarks in the mailmerge main document will have been deleted from the output.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]