try setting the wall that separates the room from the corridor to cast shadows and set the the walls in the corridor to accept shadows in the layer material properties (also, the light will need to be set to cast shadows).
that way the separating wall should block light to the other surfaces and give you what you are looking for.
You could try twirling down the layer settings for the corridor layers and go to material options then find "accepts lights" and check it as "no". You will probably then have to adjust the color of the layers to better suit the lighting.
Another thing you could try is using spot lights as you can actually aim them so theyre just affecting the room itself and you could even have some of the light "bleed out" into the hallway for a more natural look.