Error Message with my SUMIF Formula
I'm attempting to do a simple SUMIF formula, summing up sales per month. This is the formula I'm using: =SUMIF([Contract Date]1:[Contract Date]51, MONTH(@cell) = 10, [Cost of System]1:[Cost of System]51). The Contract Date is the column that has the date and the Cost of System contains the sales figures I want to add up. This example shows me trying to add up sales for October (Month 10). However, I keep getting #INVALID DATA TYPE. Can someone help?