TOPIC: Different price # of registrants

I would like the system to charge the first 50 registrants at one price, then the second set at another price.

The only way I thought I could do this is to create 2 different 'events' , Price A, and Price B., making only A active, once A is sold out, then make B active.

The problem is this wouldn't be automated, so once price A is sold out, I will have to manualy activate price b.

Can this already be done with dtregister?

This is for the joomladay nyc event by the way...

thanks,
Laura