Perhaps you should have looked at the link Graham provided...

Moreover, you don't even need to use wildcards if all you're concerned about is digits! Simply use:
Find = ^#
Replace = ^&
with the replace formatting set appropriately. But then, numbers don't always consist of digits alone - thousand & decimal separators are quite common. And dates use digits, too, but aren't numbers...

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]