Some employers will hire you after your interview and then ask you to take a drug test immediately. Others will schedule you one shortly after (maybe 2-5 days depending on how fast they need you) so this will buy you some time. There is no way of knowing for sure what this employer will do. If your going to dilute then you must buy as much time as possible and start exercising. Abstain from smoking and pick up some metamucil, this will help to excrete thc metabolites through your colon. Keep your body hydrated as you workout but you dont need to overdo it.

As I said earlier read the dilution sticky at the top of the forum it has all the info you will need. You must follow it to a T to ensure the best chance of passing.

I believe they will test you no matter if your on your period or not. Also pick up some home test strips and start testing yourself to see where you stand.