Dont quite see why you would do that. It'd be pointless. If you dont want a baby and you are sexually active you need to sort out long term birth control.
What are the odds of that preventing pregnancy? Probably VERY slim, your body has to have time to get the B/C in your system, that can take up to a month. And it's pointless to take BC for two days then stop, if you're having sex, birth control should be an everyday thing, not a once in a while thing.