Get some piss cleaner.. I hear urineluck works. This may be hard to believe, but i once passed a piss test by taping a doosch bag to my thigh and emptying it into the cup for the test. It was probably there for 2-4 hours though, and not too comfortable... "desperate times call for desperate measures" but still, this is a better bet then what you are talking about doing.
Good luck.