Jim
This is oft asked and indeed Access has it. It would be good to apply it a little like a format only, of course, it would need to make the data change whereas a format just changes the display.
It would be handy for decimals (which you can actually do now), commas (or whatever your comma seperator is), telephone numbers, (but that needs localising), times and dates especially. That's very often asked.
It should not, IMO be automatic though, like 1-3-7 get converted automatically to 1st march 2007 (01/03/2007). So user set by perhaps named range or pre-selection???
Regards
Nick Hodge
Microsoft MVP, Excel
Southampton, UK