What I mean?

I have a drilldown table where detail level has a different layout
than the grouprows (which the table header refers to).

Header:         Text               Total        Num        %
Group1         Toplevel aggr.     100         20         20
Group2         Lowerlevel aggr     50         5          10
Detail header    I would like a header row that will toggle with the
detail row
Detail           The detail level contains details about a task which
do not apply to the headers

Initially only the Group1 row is visible. When toggled, Group2 becomes
visible. When Group2 is toggled the detail row is made visible. As the
detail row does not have the same layout as the group rows I would
very much like a detail header row as well.

I am not sure this is doable (at least I haven't found out how) but it
would be very convenient for the users...