I sell weekly casino shuttle tickets and need to cut off sales when seating max is reached

I have a form set up with multiple casinos to choose from. Riders can choose their shuttle ride date and also choose to register up to four other guests to sign up. How can I cut ticket sales off at 52 seats maximum for each casino trip offered on each date I offer the trip? I have tried both the quantity gift registry and ticket inventory but they aren't doing the trick. 

Here is our casino trip page: 

http://www.goodtimegetaways.com/Goodtime_Getaways/Casino_Trips.html

In case anyone else comes across this thread, here are the widgets suggested for limiting the number of possible times an item can be selected:

http://widgets.jotform.com/widget/inventory
http://widgets.jotform.com/widget/quantity_gift_registry
http://widgets.jotform.com/widget/gift_registry

Here is how the inventory widget would look with your specifications:
https://form.jotform.com/61375991113962