I was wondering if you need to commite to the AF when you apply for OCS for a pilot position?

In other words, is there a way to apply for a pilot position and find out if you get a slot before you commite to the AF?

I know many people may think im looking at this wrong, and only want to get into the military if i can become a pilot. But I think this would give me opertunity to apply for other services if not accepted in one.

Thanks!