GUI (Tkinter) and "cancel"

[Thomas Thiele]

Hallo!

I have a simple graphical user interface written with Tkinter. This
allows a user to call a function by pressing on
a button (or something like this). The function  works for some minutes,
somtimes up to an hour.
How can I implement a "cancel"-button that allows the user to cancel the
time-intensive function.

At first I thought on creating another thread, but it must be simpler.
How?

Thanks Thomas