SSRS grouping

Hi,

   I have been searching the forums but could not find a solution. I have a row group that is grouped on by id and i have a details group. So the report would look like

ID1 --- row group

comments on ID1  ---- details group

ID2

Comments on ID2

But i could not get the details group to be grouped by ID. What i am getting is

ID!

ID2

Comments on ID1

Comments on ID2

And the picture of the grouping looks like

So in the above picture, how to get the details group with in the row group.

Thanks!