Zipper help!

[andromedagrlie.livejournal.com]

So the zipper on my boyfriend's nearly new favorite sweatshirt broke and I want to know if I could even try ti fix it for him without replacing it. It's the typical broken zipper I've seen; i.e. it will zip as in the zipper passing along the track up the sweatshirt but the teeth don't actually bind together. Any ideas? Thanks.