dynamically generate gridview inside another gridview

dear all,
i want to display hierarchial data in nested gridview. My question is how can i add a gridview dynamically within a gridview??????
i retrieve data like below
a-1 + b-2 + c-3               ( which mean a is the empname and 1 is the empno )
aa-11 + bb-22 + cc-33
aaa-111 + bbb-222 + ccc-333

i want to display the above in a gridview hierarchial like below
+a
+ aa
+ aaa
on click of a
-a   1
    - b 2
        -c 3
on click of aa
-aa   11
    - bb   22
        -cc   33

on click of aaa
-aaa  111
    - bbb  222
    & ...