I am trying to auto populate a cell with sum of users for last month:

Column A Column B
Month No of Users

I have managed to calculate, this weeks, last weeks and the last 30 days
total of users using a variation of:
=SUMIF(A1:A100, "="&TODAY()-7, B1:B100)

I want to be able to see the last calender month total. So today I would get
the total number of users for November.

I have tried adding the MONTH function but the SUMIF function does like all
the arguments needed to calculate the what last month was.

Any help would be appreciated.
-
Jeff