On Jul 10, 10:12*am, "Skinman" wrote:
This works for me =IF(COUNTIF(C$1:C$20,A1+B1)<=1,"TRUE","FALSE")
Enter this Formula validation into Range A1:A20 and the same formula
validation for Range B1:B20
If a value is entered in A or B that totals the same as any previous total
in C it will come up with error code.
Let us know how you get on please.
Skinman

That solved my problem. Thank you very much. Some day I hope I
understand it.

Warm regards from Florida USA...