Drill behaviour in report studio

[cognos05]

I have a data item with an expression  children of a member from  product hierarchy in rows.
Hi All,
I enable drill down behavior from data menu.

Now the issue I am facing is even though I start from showing a children of a member when drill up is done at this point it goes to the parent and so on the upperline of hierarchy.

If I disable drill up for this children(member) data item then any of the drill up for this member is not working.

I dont want to drill up above this level .

Thanks,
Nithya