Setting up an AutoCorrect entry for this would cause nothing
but troubles in use of Office products. Don't do it.

Widening the column was specifically rejected in the original
post.

For Don's suggestion, you might as well make that
target.value = application.proper(left(target,3))

more information on event macros in
http://www.mvps.org/dmcritchie/excel/event.htm
be sure to limit the scope of the macro to a specific column(s),
and not update row 1 descriptions.

If you had the means of obtaining an actual date, you could
use custom cell formatting. mmm which would affect
display and not the value.
---
HTH,
David McRitchie, Microsoft MVP - Excel [site changed Nov. 2001]
My Excel Pages: http://www.mvps.org/dmcritchie/excel/excel.htm
Search Page: http://www.mvps.org/dmcritchie/excel/search.htm

"Jason Morin" wrote...
set up AutoCorrect entries (go to Tools
AutoCorrect Options) and set up each month so that it's
replaced by its 3 char. abbreviation. For example,

Replace: December
With: Dec