using selective summary data to do percentage

[jmfox2]

I am working with data like this (minus the %change col). The data below are summarized groups within my crystal.

DRG fy fyfq Cases AChrgs % change
level1
99999 2001 200101 33 8,584
99999 2001 200102 32 7,825
99999 2001 200103 43 7,491
level2
99999 2001 Tot 43 7,924

level1
99999 2002 200201 39 10,090
99999 2002 200202 33 11,358
99999 2002 200203 44 11,810 0.576
level2
99999 2002 Tot 44 11,103 0.401

level3
99999 Tot Tot 44 9,570

I need to be able to do the following calculation for current qtr (3rd) and for drg total.

(curr 3rd qtr chrgs (11,810) - prev yr 3rd qtr chrgs (7,491) / prev yr 3rd qtr chrgs (7,491)

then do similiar logic to compare current year to previous year total. Thxs, jmfox