Hello... I hope that someone can help me.

I have a worksheet for which I randomly enter scores for students in
several categories throughout the day.

Column Headings:

Date StudentName Category1 Category2 Category3, etc.


I would like for Excel to display a warning message if I attempt to
enter a score in the SAME category on the SAME day.

Does anyone know how I may do something like this?

Thanks!!!
Jessi