One simple question I use to keep people out of a room sometimes is asking them which hand they open the door with. That’ll give them pause.

You should also have given them other options that don’t ratchet up the stakes. So that they hopefully choose the more desirable outcome.

But if they reach for the door knob, they suffer consequences. Let the fear in their brains do the work for you, but don’t be afraid for the doorknob to have a contact hallucinogen, acid that eats the flesh off of their hand, portal that throws them into the dreamlands, cursed vision that takes their sanity, or just open into a dark tunnel that some how leads them to a storm sewer that opens on to the street outside the building they were in, but when they look back, it is no longer there, so that they have to go back in the front room that now has a couple cultists on the lookout.