How to make server avoid joining through the normal "Play" button through scripts?

I want to lock a server but not just kick the person who tries to join. I want it to just make a new server as if the locked server didn't exist. Is there a way to do this with scripts? Or is a reserved server my best bet? Kind of like if all the remaining slots were suddenly reserved slots, only can be used by joining directly.

Best shot is probably reserved servers, unless I'm missing something.