Spindrift
I'm sure David's answer is the way to go if you want to validate data. To complete the answer, Access has 'placeholders', Excel does not.
You could also use a Worksheet_Change() event to validate the input into a cell and if you could validate as a date (4, 5 or six numbers not exceeding 28, 29, 30, 31 and 12 in the right places, etc) then format it as one?
Neither solution is like the placeholder functionality in Access, but both offer solutions.
Regards
Nick Hodge
Microsoft MVP, Excel
Southampton, UK