I do know of a way to accomplish this without scripting or apps, but it is quite complex, and by no means easy to explain in the text of a forum post.
I don’t really have the time to explain it, but I’ve crafted an example in this base:
The tables you are concerned with are:
You will find that they are related in such a way that the
❓Availability table is used as a querying table where a Site Type and desired dates can be entered to surface Available Sites in the “Availability Check” view of the
⛱ Sites table.
Frankly, my honest suggestion is to use Kamille’s excellent Marketplace App. Since it’s in the Marketplace, installation and setup should be a breeze, and you won’t have to do any scripting.
Alternatively, I have a much simpler Custom App than Kamille’s that only watches your table and detects scheduling conflicts, making them apparent and easily accessible in from the App. I’d be happy to provision this app into your base, if desired – but you’ll find Kamille’s is much more fully featured.
Here’s a little gif of that App in action: