Try this:
If the input cell is A1 . . .
=SUMIF(B13:B28,IF(ISBLANK(A1),10,A1),P13:P28)

Does that help?

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Regards,
Ron


"Rick" wrote:

I currently have a cell that has the folowing formula
=SUMIF(B13:B28,10,P13:P28)

Is there a way for this cell to allow a manually input value and if none
then utilize the above formula for an automatic cell value?

What would the formula be?