Oh. The only way to do that is by setting up custom record selection filters. Plus, I think you'll have to do subreports to get totals for each grouping. Actually, you could avoid subreports by making a more complex record selection formula, but it depends on your CR skills.
LastMonthMTD (something like...):
Date(Year(DateAdd("m", CurrentDate, -1), Month(DateAdd("m", CurrentDate, -1), Day(CurrentDate))
LastYearMTD (something like...):
Date(Year(DateAdd("y",CurrentDate, -1), Month(CurrentDate), Day(CurrentDate))
I didn't test any of these. Just typing them in off the top of my head. So you'll probably have to tweak them to make them exact.