When do new employers make you pee?

OK. Before I get yelled at for not looking I did. I spent a few hours brushing up on how to try and fool my UA. I just have a few questions that hopefully you experienced guys can help me out with.
I am moving to Denver to get a new job in a day or so. I'm going to need to take a drug screen for my job. I've smoked maybe 3 times in the past 2 weeks. Before that maybe a hit or two every other day. The last was about 6 days before i think I will need to pee. I purchased one of the bottles at a local head shop, its called Vale4x. I then read that I could have saved my money and done it myself but whatever is done is done. After reading today on this board I went out got me some creatine, asprin and tums.
My question is this. How does the screening work when I show up for my first day? Are they going to make me go into the bathroom and pee or will they send me someplace to do it? I need to know when to take to bottle of stuff. I've started taking my creatine, I figure a little more than what they say to take a day should build up enough in my system. I plan on drinking water nonstop until then just to be prepared to have a diluted sample whenever. (that and I need to drive cross country 1800 miles, so my constant need to pee will keep me awake ;) )
I'm about 5'8", about 180 with a little love handles but I also work out 3 times a week so I'm not a total fat ass. Any experience with this product? Should I do anything else to prepare?

Sorry, I also forgot to add... Does anyone know what the laws are in Colorado for drug testing. I know that the state I live in they cant watch you for a pre employment screen. (Or so I've heard) Is it the same for Colorado? Would I be better off returning my bottle of stuff in exchange for fake urine? I'd rather not use the fake stuff if I have a better than good chance of passing with the dilution method and the Vale4x. Any help from what appears to be a rather smart group of potheads is greatly appreciated. Thanks in advance

Your proballey safe with just doing a bit of excercise and dilution Im pretty sure in every state there not allowed to watch you pea (well your employer, not sure about other things unrelated). Ive heard those drinks to work but subbing is pretty much 100% guaranteed. I just ordered Quick fix and im gonna try it out for the first time in a few days when I have my test.

How do you make your own detox drink anyways?