Take a look at Data Validation in XL Help.

In article . com,
"Resant" wrote:

Hi All,
How to empty the cells if the input doesn't pass the validation.
Eg :
The entry must be 'A' or 'B'.
If user try to entry 'C', they will get error message and I want empty
that cells.
How to do that?

Thanks,

Resant