Changing Column Labels dynamically

[Steve]

I have a report written in Report Studio. It's like this:

Products                   Revenue              Cost           Margin        Accounts
-----------                   -----------          ----------          ---------      ------------

Notebook Computer   12,000           10,000            2,000            120

The dimension Products has 5 drill down levels.  For the 1st two levels, the last column 'Accounts' should say 'Accounts' and for the last 3 , it should say 'Subscribers' . How can we do this? By making a Report Expression?

If yes, what kind of expression will it be? I can't seem to figure out how to determine which drill down level is the user currently on?

Thanks,
Steve