I have a spreadsheet that calculates a total (Cell N75) from several other cells (O2+N79-N77) which is a sum of a range of cells (a72:k72) I need a way to be alerted, such as a message box, when the total of N75 falls below 0 or rises above 96. I've tried several custom formulas (=AND(($O$2+$N$79-$N$77)>=0,($O$2+$N$79-$N$77)<=96) in the data validation field, but none seem to work.
I've tried this in the cells where the data is entered, where they are calculated, and in the final cell, N75.

Anyone have any ideas?

thanks!