SQL Query - Group By Month End Dates

[FizzyFish]

How do I group weekly data by a MonthEndDate?

Ie. WeekEndDate are 2007-02-10, 2007-02-17, 2007-03-03, 2007-03-17

I need to somehow group these so they show the data as sums for 2007-02-29 and 2007-03-31

Thanks!