Group by Option is not working if header having more than 2 levels

[krg2000]

Hi,

I have two problems.
1)In my Grid header contains 3 levels like A/B/C . If i use group by option on C then it is not working. Please help me in resolving this issue.

Header Level 1 -  A
Header Level 2 -  B , C, D coulumns
Header Level 3 - below B column one more column X, Below C column one more column Y like that
If i use X column for group then it is not working.

2) How to change the css for header only.