Event Registration with Paypal and complex customization

I’m looking for an event registration plugin with paypal integration to pay for events. I offer classes as a bundle. I offer 8 classes of which users can register for all 8 (which is not a problem because I have 8 pre-determined dates). However, I also let people sign up for 4 class packages with the ability to allow the clients to pick any 4 of the 8 dates to attend. I have a limit of 10 spots per class. So if people register for 4 classes, I want them to be able to select any 4, but as they pick from the available dates, I only want those dates to be reflected in the amount of spots remaining on the calendar. I’m hoping a plugin exists that has this functionality … anyone out there ever see such a plugin?