You would probably have a fair chance with dillution. Read the dillution sticky and follow that the morning of the UA. Drink gatorade instead of water. It would still be a good idea to pickup a test strip and test yourself to see if you pass.
There is really no way to guage when someone will be clean, there are just too many factors that make the time vary.
If you fail the test its only kept on record at thatiness you applied at. Businesses are not allowed to share medical information about employees. Its against the law.