Tkinter event loop question

[gordon]

is it possible to send a message to the gui instance while the Tk
event loop is running?I mean after i create a gui object like

root=Tk()
mygui=SomeUI(root)

and call
root.mainloop()

can i send message to mygui without quitting the ui or closing the
window?i tried some code like
mygui.someMethod()
but it only gets executed after i close the the ui window.Is there a
way to get this message passing while gui is running ?

(forgive me ,it is a repeat question..but i am a bit desperate)
thanks
gordon