help with _invalrect

[berger@SOE.Berkeley.Edu (Daniel Berger)]

How do you get _invalrect to "invalidate" a rectangle of a view?  In the manual
there is an example on how to "invalidate" the window.portrect, but I am
unable to get it to work for another programmer specified rectangle.

Also, is there a way to find out what are the rectangles that are "invalid"?

Thanks
Daniel