grouping to form tree view

[grouping]

i am using crystal reports 8.0, i have a table called subjects having fields subjectid, description, parentid. i have another table called cases which has caseid, subjectid, description.

Now i have been able to group on the subjectid column of subjects table and get a tree view. also in the group i get the number of cases associated with the subject id.

but my problem is i cant get the count of the cases associated with the lower level subjects in the parent subjects??

ANY OF YOU GURUS OUT THERE??