You are not going to be able to format the field in Word while the 'A' is
present in the number. Create a new column in the Excel table and separate
the number from the letter, then you can combine the fields to produce the
layout eg
{MergeField MediNumber \# "000'-'00'-'0000"}{Mergefield Suffix}

See http://www.gmayor.com/formatting_word_fields.htm

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Graham Mayor - Word MVP

My web site www.gmayor.com
Word MVP web site http://word.mvps.org


Code Doctor wrote:
I have in Excel a text field that contains unformatted Medicare
numbers, ie 123456789A. In a mail merge, using that field, I want the
display to look like 123-45-6789A.