How to use iMovie to Block out a portion of the video

Hi there;

Is it possible to "block out" a rectangular region(s) of video using
iMovie? I have the latest (v3) with my iMac and have a customer with a
video that has an address and phone # at the end. I need to block over
that old phone # and address to put in a new one and am wondering if
someone has a great idea on how to do this.

I am thinking maybe some sort of weird text title might do it but does
anyone else have a better suggestion that might work and not be so
painful?

THANKS!!!