Total Label in Drill down reports

This is a simple case scenario. I created one drill down report by Country --> State --> City and set this object as section. It has revenue Column in it. Now I did Summation on the Revenue column and it shows like this

USA -- (Section)

Column1, Column2

XXX, 3

Sum, 3

Now instead of Sum, I would like the label to replace it with country name and when I drill down to second level, it should replace it with the State name and again on level 3 replace it with City name.

Could anyone help me on achieving this. Is it doable? I have been trying to achieve this but had no success.

Thanks for your help in advance.

Rids