=text(a1,"00000")

or use Word field formatting codes:
Mail merge Excel to Word:
a.. http://www.mvps.org/dmcritchie/excel/mailmerg.htm
b.. http://www.mvps.org/word/FAQs/MailMerge
c.. http://office.microsoft.com/en-ca/as...164951033.aspx
d.. http://sbarnhill.mvps.org/WordFAQs/C...ngWord2002.htm
e.. news:microsoft.public.word.mailmerge.fields

--
David Biddulph

"Cheryl" wrote in message
...
Office 2007 - used spreadsheet to create an address list; zip codes appear
correctly in spreadsheet but when using spreadsheet as a mail merge
document,
the first digit disappears in the zip code field, i.e., 05401 becomes
5401.