Hi,

I am working on a spreadsheet where I am using sumproduct to conditionally count instances of certain contracts.

This spreadsheet will be populated every month by field agents -- I want to build something into the spreadsheet where the agents can only enter into the cell certain single letter values or a valid date.

For example, they can only enter "X", "J", or "M", or a date.

I can either stop them from entering invalid options or I can reflect their error through a sum-product formula. But i'm not sure how to do either.

Any advice will be appreciated. Thanx