Rows are making errors in formula

Hello, I have the following formula: SUMPRODUCT((YEAR(Breakdown1!$N$2:$N$155)<YEAR('Capacity v Demand'!C$1))*(Breakdown1!$O$2:$O$155='Capacity v Demand'!$A2)*(Breakdown1!$P$2:$P$155))

On the Breakdown sheet the number of rows is constantly changing. With the number of rows constantly changing I am getting #VALUE errors. in the capacity v demand work sheet. I'm not sure how to change my formula to accommodate for the changing number of rows.

Thanks in advance

Hi
the easiest way is to use Excel Tables

You could also use INDIRECT to build the target range. Count the number of rows with data and concatenate the target address into INDIRECT