For each ticket, you can determine when your visitor can enter the event. Using multiple tickets, you can assign different time slots to various target audiences. The tickets can be scanned to check-in your visitors during the indicated times.

You can enter the appropriate times in the Ticket Module. Select a ticket and determine the start and end time at the column 'Time slot for scanning tickets.' Now, the visitors with this ticket can only be checked in during these specific times.

Read more about checking in visitors.