Correct column calculations for groups

I am grouping a table on a calculated column (week number) and calculating sums for each of the remaining columns. Each group has a row at the bottom with the sums but the sums are for all of the groups instead of for each individual group.

So the result looks like this:

week: 27
Date Col1 Col2 Col3 Col4
07/02/2012 12 5 10 7
07/03/2012 12 4 10 2
07/04/2012 12 4 10 3
Total SUM 39 14 33 14

week: 28
Date Col1 Col2 Col3 Col4
07/14/2012 3 1 3 2
Total SUM 39 14 33 14

Has anyone found a way to sum by group instead of by everything? My client doesn't really care about the "Grand Total", just weekly totals.
Thanks!