Problem with tkinter mainloop

[k2riddim]

Hello,
I'm a beginner with Python and Tkinter development.
My application parse links in an html file. And I use Tkinter to
implement a GUI. This GUI has a button to launch the parse treatment,
and a status bar to show the state of the treatment.
I know that because of the mainloop, my tkinter application freeze
while my treatment isn't finished. That's why my status bar doesn't
update herself in real time.
I wanted to use the after or the after_idle function, but I don't
really understand why it doesn't work.

My apps is build approximately like that :

---Gui.py---
class Gui(Frame):
        def __init__(self):
                ...
        def launchTreatment(self):
               b = Treatment()
               self.after(b.treatment.parse)

---Treatment.py---
class Treatment():
        def __init__(self):
                ...
        def parse(self):
               ...
               GUIinstance.status.set("state 1")
               ...
               GUIinstance.status.set("state 2")


---Main.py---
#instanciation of classes
GUIinstance = Gui
GUIinstance.mainloop()

Any help will be very appreciated, excuse my english, this is not my
native language as you can see.