I need an extension to be developed for my website, which will show the customer an option to choose date and time slot for his delivery. The extension should give me the flexibility to customize from admin the number of time slots per day, number of deliveries per time-slot, manually block a date and/or timeslot. Also, time-slots should get blocked based on certain cut-off time logic. i.e at 7pm today, i want tomorrow's first 2 timeslots to be blocked. This should also be made customizable.