I need advise ASAP

I need to pass a drug test on 10/15/12 for a new job. I'm a chronic smoker and have been for the past 4 years, some days maybe just a few hits. What should I do? I've never had to take a drug test before and dont have enough time to naturally detox and im too nervous about using a sub (although Im still considering it). I've been exercising almost every day this past week and on a very low fat diet, but I'm 5'4 and weigh around 160lbs. Any advice would be greatly appreciated!