I got part of it!!

I realized what was wrong with my formula and modified it. It seems to semi-work now. Here's the formula I entered in the data validation (under custom):
=COUNTIFS(ref!P:P,"<="&temp1!M3,ref!Q:Q,temp1!O3) +COUNTIFS(ref!R:R,">="&temp1!N3,ref!R:R,temp1!O3) >= 1

But before, my cell temp1!O3 used data validation to provide users with a scroll down option to select their location. I had to replace that with the above formula. Is there a way to have both operate? ? The data validation for the list and to have this formula to help prevent duplicates?

Thanks!

Geoff