You can do the formatting on the Word side by adding a format switch to the
merge code: The text below is verbatim from Word Help. Search form "Format
Merged Data" in Word help for the complete topic:
To control other aspects of formatting, press ALT+F9 to display field codes
(field code: Placeholder text that shows where specified information from
your data source will appear; the elements in a field that generate a field's
result. The field code includes the field characters, field type, and
instructions.) in the main document, and then add switches (switch: When
working with fields, a special instruction that causes a specific action to
occur. Generally, a switch is added to a field to modify a result.) to the
merge fields.
For example:
To display the number "34987.89" as "$34,987.89," add a numeric picture
switch (\# $#,###.00).
To display the number "0945" as "9:45 PM," add the date/time picture switch
(\@ "h:mm am/pm").
To ensure that the merged information has the same font and point size you
apply to the merge field, add the \* MERGEFORMAT switch.