R help - Aug 2006 - tcltk command to figure out which widget is on focus (or clicked)

Hi,
I'm making an interface, where a Tcl/Tk window have few listbox widgets.
I need to select separate parameters from separate listboxes.
It is clear how to get cursor selection value, once you know which listbox
widget you clicked.
The problem is I can't figure out which one tcltk command to use to get an
information which listbox widget is in focus (or clicked).
Thank you,
Vlad