Zooming in on footage

Hi all, i feel like a bit of an idiot asking this question, but as this video project is my final work for high school, i cant put it off any longer.
Im using premiere pro cs3 and attempting to zoom in on a section of footage.
Now i know the "camera view" effect allows you to zoom in on the center of the frame, but how do i change the target of the zoom.
For example, someone is talking and i want to cut to a closer shot of their mouth, but i dont know how to get closeup on their mouth and not the frames center.
Im sure the answer is sitting right in front of me, ive been using premiere pro since 2 first came out, so i really do feel like an idiot.
Thanks in advance
-Dave