Howdy Alex,
That is a cool idea. A few people have requested that we add a booking feature to our calendar. This would allow them to set how many overlapping events can be created for a given venue, which in your case would be only one. This is not currently a feature of The Events Calendar, but we are considering building it.
Have you seen the official feature suggestion (click here)? If not, you should open that up and see if it sounds like something you’d be interested.
Unfortunately there are only two solutions available right now. You can wait for us to build that capability and add it to our plugin suite which will take at least a few months to build. Or, you can build it yourself. If you wanted to do something incredibly simple, it might be possible with only a few hours of work. Using the WP API you could tap into save_posts, run a query again the currently selected venue and times, and see if you get any results. If you do throw a WP save error. It won’t be super fancy, but from the sound of your needs I think it would get the job done. 🙂
Does that fully answer your questions? Is there anything else I can help with?
Cheers!
– Brook