You don't give us too much to go on. This sums column B if the corresponding
date in column A is in Q1
Change =1 to =2 for Q2 wtc
=SUM(IF((INT((MONTH(A1:A100)-1)/3)+1)=1,IF(A1:A100<>"",B1:B100,0)))
This is an array formula which must be entered with CTRL+Shift+Enter and NOT
'just enter. If you do it correctly then Excel will put curly brackets around
'the formula{}. You can't type these yourself. If you Edit the ranges
'then you must re-enter as An array
Mike