How to create a modal dialog in tkinter?

I have a MFC application which runs some embedded Python scripts. I am trying to make one of the dialogs this embedded script creates modal, but I am not having much success.

Can anyone point me the way to make a modal dialog? Do I need to use a windows functions for this or only Tk or Python functions are enough?

For what I googled looks like the following combination of functions should do the magic, but they dont seem to work the way I was expecting:

focus_set()

grab_set()

transient(parent)