Yup - I just ran into that when I tried it on my full data set! I had to
use =year(A1)&month(A1) and work with it that way to get unique months for
each year that could then use the sumif and countif functions.

Thanks for all your help Jay!

Heidi

"Jay" wrote:

Try putting these in row 1 and copying down for as many rows as you
need.

C1: =IF(E1=E2,"",SUMIF(E:E,E1,B:B)/COUNTIF(E:E,E1))

D1: =IF(F1=F2,"",SUMIF(F:F,F1,B:B)/COUNTIF(F:F,F1))

E1: =WEEKNUM(A1)

F1: =MONTH(A1)

The averages appear for the last day of each week or month.

Thank you Jay! That is exactly what I was looking for!

Two words of caution, though.

1. If your data spans more than 51 weeks, there'll be a problem because C1
goes by week of a year.

2. The calculation assumes that the week containing New Years Day is meant
to be split in two.

Adjustments for these potential pitfalls are straightforward. ;-)