if your that worried then dont smoke for a few weeks, also i think borders book store doesn't drug test and maybe barnes and noble doesn't either?? but if you want a better job and refuse to quit then go work at burger king until u decide otherwise. I have a friend in a similar situation, he just started working and he's 20. He's working at a fast food place and is always complaining about his job and wanting a better job, but he refuses to quit for a few weeks to get a better job, so i dont feel sorry for his ass at all.
Just think of it this way, most jobs will only give u a pre-employment drug test, just pass that and u can smoke up again. Cheers.