Grouping/toggle middle column of report

Hi

I have a report that is 6 columns along, is it possible to have a group/collapse/expand button on say the 4th column? Everytime i grouping it seems to inpose a toggle + on the left most inner column.

I'd ideally like this on the 4th column, when you press the + button it then drills down to show the 5th and 6th columns.

Any help is appreciated.

Cheers