Data Validation formula

[DustinS]

Using data validation, I would like to have the user be able to select (or
enter) either "XXXX" or enter a four digit number. How can I do this?

 

[Chip Pearson]

Dustin,

In the Allow box, choose Custom, and use the following formula.

=OR(A1="XXXX",AND(ISNUMBER(A1),LEN(A1)=4))

Change A1 to the appropriate cell reference.

 

[DustinS]

Chip,
When you have a moment would you be willing to explain why that formula
works the way it does?