If my rating is 1799, I may enter a tournament with range 1500-1800. But, what if I am the first person out of 5 to enter the tournament, and then my rating goes up from 1799 to 1810 -- does the logic get re-applied when the tournament starts?

Help! 

http://www.chess.com/forum/view/tournaments/ratings-and-tourney-acceptance

Appears you would be dropped.

Ah, so it goes by tourney start, not when you register.

Thanks for the reply.