We want to be able to limit a user to only be able to make one purchase of one product up to a total quantity we can set. Imagine it as selling tickets to an event, you can purchase up to a certain limit of tickets to an event and then not be able to purchase any more after completing the purchase. Our products are timeslots for a specific event so we want to allow people to register and add the qty of tickets they need to their cart, confirm, then not be able to buy any other tickets.