George, this question gets asked from time to time, and the general
concensus is that there is no input mask that matches phone numbers from
different countries. Further, countries change their phone number systems
from time to time, so it might be a nightmare to keep up to date if you did
go to the trouble of developing and applying custom masks specific to each
country.
For previous discussions, go to groups.google.com, and search
microsoft.public.access.* or comp.databases.ms-access for threads with
"phone" and "input mask". If you get too many, filter to those authored by
Brendan Reynolds. (He's from Ireland.)