I'm having trouble creating the formula for this requirement:

This is what i came up with:
IF 'SYS01 Time Settings By Week'.'1st Forecast Year?' THEN OFFSET(Volumes, -52, 0) ELSE 0
My model is taking this formula without error. This might be a silly question, but how do i check if this is correct? Here is what my module looks like (grid view, bp view):


Thanks in advance.
-Paul