Alternatively to the answer posted below. Launch Word. Go
to Tools; Options; General. Select Confirm conversion at
Open; OK. Follow the usual procedure to create your mail
merge. Once you have selected your data source, a dialog
box will appear. Select MS Excel Worksheets via DDE
(*.xls); OK. Proceed with the mail merge as before. When
you preview your individual letters, the numeric data will
retain the formatting as per the data source