Seat Limit Capacity

Hi, May i know is there a way that I set limit for one specific field. For example, Im doing a seat reservation daily and opening 4 timeslot(6,7,8,9PM). I have multiple zone in my arena. And in Zone A there is limit of 40 people, The user can key in their PAX. So when the total record of PAX field sum up to 40, it will popout “this zone is full”. I dont mind to pay in order to get this feature, please help.