Kivy--how to bind a function to a checkbox when activated

I have a Python program in wich I use kivy's checkboxes.

Is there a way to let the program call a function the instant when the checkbox is disabled/enabled? please note, the active property wont work since this is only once, one would have to use a infinite while loop to check whether the user activated it wich would make everything complex.

so anything that can help here welcome

Thanks and regards

Cid-EL