Slipping him your number doesn't sound like a bad idea. The best way to get to know someone is one-on-one confrontation. You could do other things other than slipping him your number, such as a note for the days you're off work, or time you get off work while he is at the bank. That would be at least showing him some interest, and giving him a chance to make his move, although I say your best chances to get to know him would be just slipping him your number. That would rule out relying on him asking you for it. Those are just a few suggestions, the possiblities are endless. Choose what ever fits YOU the best!
Impossible is a word only to be found in the dictionary of fools.
Napoleon I