Using the same Data set from a subtotal formula to put into a sumproduct formula

I have a spreadsheet with Subtotals already in it. I've come up with this formula:
=SUMPRODUCT(SUBTOTAL(9,OFFSET($V$3,ROW(V4:V4)-ROW($V$3),0))*(R4:R4=$B$1))

Which I inserted in the cell next to the subtotal formula:
=SUBTOTAL(9,V4:V4)

How do I repeat the SUMPRODUCT formula so it has the same data set range that the next SUBTOTAL uses?