I am trying to have my spreadsheet sum up purchases that fall between (month)
12th to (month) 12th, and when/if a new purchasing month starts, restart
summing the purchases. Column G are purchase amts. Column A are purchase
dates.

Originally, I just referenced month to month, with Column I formula:
=MONTH(A5) etc., and my running total forumla:
=IF(I4<I5,G5,IF(I5=I4,(G5+J4),0))
but because my purchasing dates are middle of the month, this is not working
so well.

I would like something I can fill down and not have to rewrite for each date.
I've looked through the discussion threads trying to figure out what might
work for me but haven't found anything.

Thanks in advance for your willingness to help!