Hi,

I need help with a formula to add the sum of values in column D if a date in
column A is between 31-60 before C1 (A100), or between 61-90 before C1
(B100), or between 91-120 before C1 (C100) and so fort.

Example:

C1= 10/31/08

A1=8/31/08 D1= $1,200
A2=9/30/08 D2= $1,200
A3=9/30/08 D3= $1,200
A4=10/31/08 D4= $1,200

A100= Total of 30-60 B100= Total of 60-90 C100= Total of 90-120