PixelChecksum, explain it to a dummie?

So if I got PixelChecksum correctly, it can check a square of pixels on a window. Can I somehow use this to invoke a forced continuation of the script?
An example:

I have one window where the pixels will be the same for an unknown period of time, and suddenly changes.
Instead of using Sleep(x) I want the script to recognize when the pixels in the window has changed, and then continue executing. Is this possible with PixelChecksum?

Also is it possible with any kind of reliable way to get the ControlHandle of a Window and store it as a variable? I can only get it through the AutoIt Window Spy.

Thanks!