jcarp - Yes, I used an interrupt-handler similiar to this the first time through. The basic problem though is that the process to change the vertices takes a ton of cycles so the scale action is pretty erratic. Thanks for passing that along, it is appreciated. Turn-about is fair play so take a look in the Grayson book at the 'after' method. (Lutz - Programming Python has a better section on it.) I've recently started using it with scales and it works quite well. No Go! button to activate a process and the scale runs free so it's fast.