I'm having trouble with my validation formula. I'm wanting to check for duplicate invoices and I am using this formula:
=Countif($C$9,C9)=0
I have a range of cells (C9:C38) that I copied this formula to. My problem is that the validation only gives the error message if the new invoice is the same as in C9, I can put the same invoice number in cells C10:C38 and no error message. What's wrong?
Thanks,
=Countif($C$9,C9)=0
I have a range of cells (C9:C38) that I copied this formula to. My problem is that the validation only gives the error message if the new invoice is the same as in C9, I can put the same invoice number in cells C10:C38 and no error message. What's wrong?
Thanks,