Pushed For Time

I'm infatuated by a girl at school, but she's leaving soon. Two weeks to be exact. After that, she moves far, far away and I won't get to see her sweet smile ever again. Thing is, last year, she found out I had a crush on her, and I still do. I don't know her too much, and I really want to confess my feelings towards her. I'm thinking of giving her my email address and phone number when she leaves and telling her how I feel, but how could I build up a "foundation" for us in such a short amount of time?