I just want to change the products purchased report to still show the best products purchased by month obviously sorted by month with some sort of separator by month

As simple as having a subheading of month and the stats per month under the month.

Actually all I need is a report that gives me the monthly sales by product - it would be nice if it took the month as a parameter but the best products report sorted by month with the date as part of the listing is all I need

How would I modify the standard report to do this?

Any advice?