from faustus@CS.Berkeley.EDU (Wayne A. Christopher):
[C]reate the Tk toplevel window but don`t map it (wm withdraw). Then
re-parent the window to be a subwindow of your other one and then map
it. I have done this when the Tk application is a separate process,
but if it`s the same process I think you will get into trouble with the
event loop, since each toolkit wants control.