Soritng of data in BIRT report doesnt work in groups.

I have a report designed using BIRT.
Facing problems with sorting issues.

The data is displayed within groups.
The sort parameter includes the value displayed in group header.
When i select the sort parameter, the value displayed is not sorted.

For sorting to work on group header, where do u need to add the following:
params[paramSortValue].value i.e is sort expression
code,
In table level sorting.
Or under group level sorting.

Also please see the attached sort.bmp file for clear understanding.
As shown, the report does not sort the data with sortValue1.
Is this the problem because the sort filed is displayed with the header?
 sort.bmp (5.26MB)
: 3
Thanks,
Sayaly