In the cell where you want the result type =SUM(1/COUNTIF(A1:A6,A1:A6))
(replacing A1:A6 with the range where the PO numbers are) and then rather
than pressing Enter to write the formula to the cell press Ctrl+Shift+Enter

Sam

"Richard" wrote:

Is there a formula that will count the number of unique values based on a
crriteria? For example. I have a sheet of part numbers with coresponding
purchase order number and quantity received. For a number of part numbers
there are multiple receipts on a purchase order so the PO number shows up
multiple times. I want to count the number of PO's base on the Part number.
How can I do that?