Oracle 10g Graphics question

Hi

I hope I am not sending this to the wrong group, but I need some help
solving a problem.

I'm supposed to create a graph which combines two sets of data, and I
can't figure out how to do it, or if it's at all possible.

The graph has to show actual time intervals for specific transaccions,
as bars (different series possible for every transaccion), as well as
overlap those bars with a line indicating the desired time intervall
for the respective transaccion.

A simple bar/line combination graph is eassy to make, but in this case
there's under-elements in the real time-intervals, and no such for the
desired time-intervalls, and whatever I try, the resulting graph is -
to say it mildly - a mess.

I'd be gratefull for any help solving this.

Regards
Agnes