you should be fine...

i was smoking about every day in june/july and the first week of august, then took about 2 weeks off and then smoked for about 5 days strait... ended up getting an interview and had to take a pre employment test... i was 15 days clean up to the time i took it, i diluted only the start of the 2nd week b4 the test with litteraly 3 32 oz powerades and about 20 oz of water per day.... the morning of the test i drank a cpl glasses of water, pissed a cpl times and then downed a 32 oz powerade and pizzed 3 more times b4 taking the test... my pee was as clear as it could get by the way... it was sent off to a lab and i passed.. i took no vitamins to color my pee, no creatine or any of that shit, just powerade and water.... im also 6'0 / 240 and excersize none whatsoever....

i think you said youve been clean for 3 weeks, if thats the case just drink alot of powerade or gatorade and some water... about 2/3 powerade and 1/3 water...