This is not advise but something that happened to a friend. He was being tested regularly after a previous positive test. On a probation for his job. Each time he got tested he would go out that day after the test and get stoned to the bone since they were testing on an average of every two months. So after one of the tests we got him as stoned as we could. He stopped as usual but this time he got tested after 14 days. He still passed the test. So it could be possible to pass in that short of time.

However I would not reccomend doing this. Either dillute before the test or get the synthetic urine if they don't watch that closely.