Stop a duty in a Tkinter program

[XiaoQin Xia]

Hi, everybody,

I am programming with Tkinter. After the user click "Go" button or menu,
my program will carry out some operation which won't stop until the end
time (which is set by user) reach. In order to let user interupt the
operation, a "Stop" button is present. But during the period of the
operation, my program is not able to respond to any click at all, it
seems dead before the operation finished.  How can I terminate the
operation without exit the program? Any help is welcome.

Cheers,
Xiao-Qin Xia