OK, I'm getting weighed in at work tomorrow, and if I show anything more than a reasonable gain in BF, I lose 500 bucks.

My question is how fast will I lose it.

Last 12 weeks I have Lifted/Ran/Swam, etc. Also, my diet was very very strict. I gained a good amount of muscle and shedded fat away. 15% BF to 9.2% BF.

This week my diet was still strict, however, my excersize has gone down this week. I didnt play frisbee this week, ran twice rather than 4 times, and lifted just once.

In short:
12 weeks ago: 15% BF
hardcore working out/diet
Last Thursday: 9.2% BF
Since then, much less excersize, but hard diet (...except saturday :P).

Can you guys give me a decent prediction of what my body fat will be at this week?

If I am over 12% I lose.