How to bill customers automatically from MySQL table

[matth]

Hi guys, I'm working on a project that works almost exactly like most daily deal sites - when enough people signs up for a deal, it unlocks and is on for limited time.
The customers that sign up to the deal before it unlocks, would give their billing info and if there's enough of those people, the deal unlocks.

The hard part is that how can I bill the customers who sign up to the deal before it's unlocked, when the deal unlocks? Billing info would go to a MySQL table, but what then? How can I get the money from their bank account to my account automatically when the deal unlocks? I'm using Paypal for billing.

I've been struggling with this pretty long now and I can't find the answer myself.

Thank you for reading, I appreciate your time.