Is it possible to do a cutaway when using a green screen?

Hi,

I'm about to record a video of myself in front of a green screen. This video will need to cutaway to other videos and images. Is that possible with iMovie '09 or do I have to create a 'regular' video (no green screen) in order to use cutaways? I've tried adding a cutaway to a project that was created with the green screen, but the cutaway only replaces the green screen image, it doesn't actually cut away. HELP!