Bendleton wrote:
How can I create a function to return a 30, 60, 90 date average based on a
date field. In other words, if date of a row is within the past month,
include it in the avg calculation. Thanks,

-BP-

Hello,

If A1 holds your comparison date (i.e. TODAY()), column B your date
data and column C your data you like to average, then

=SUMPRODUCT(--(B1:B99-A1=0),--(B1:B99-A1<30),C1:C99)/SUMPRODUCT(--(B1:B99-A1=0),--(B1:B99-A1<30))

This is for 30 days rolling. If you need a special month, for example
December 2006 (enter any day of Dec 2006 into A1):
=SUMPRODUCT(--(YEAR(B1:B99)=YEAR(A1)),--(MONTH(B1:B99)=MONTH(A1)),C1:C99)/SUMPRODUCT(--(YEAR(B1:B99)=YEAR(A1)),--(MONTH(B1:B99)=MONTH(A1)))

For two or three months I would add two or three of these formulas.
Just take DATE(YEAR(A1),MONTH(A1)-1,1) instead of A1 for the month
before and DATE(YEAR(A1),MONTH(A1)-2,1) instead of A1 for two months
before A1.

Regards,
Volker