question option-pane

Hi all,

is it possible to have an option pane with a hierarchy instead of a flat
list?
I mean: I'd like to have this hierarchy in an option-pane:

1
2
3
   3.1
   3.2
4
   4.1
....etc

(3.1 and 3.2 are "children" of 3)

and of course I'd like to be able to choose any of the number (1, 2, 3,
3.1, 3.2,etc)

thanks,
regards,
Miro Casanova