Zooming in on part of a video clip

I'm new to iMovie and don't even know if what I want to do is possible, but i've done a few searches and come up empty, so here goes:

I'm working with a video clip of my dog playing that is about 45 seconds long. In one part of the clip she runs away from the camera, and does a funny jump. I want to zoom in on her when she jump, which is lasts 5 seconds (not the jump itself, just the lead up and landing :P).

I know that I would lose some resolution in doing this, and I'm OK with that. it's not too much zoom, maybe 25% of the original frame would be lost. Is this possible in iMovie '11?

Thanks,
psymn