i don't know of any 100% sure ways. unless you can have somebody stand in for you or sneak someone else piss in with you to use.
i understand there are some ways to help hide A/S use in tests but there are some factors to consider. what are you cycleing? are you currently using anything? when will the test be? etc.
are you sure you will be tested for A/S? if this is an employment related test, they very rarely test for A/S.
good luck. let us know how it turns out.