You could set up a trigger that says if West detected by East then in the Activation line put "Nocutscene=true". Then using F2 click on the trigger and drag it to the player, a line should connect the two. Now if your player enters the building and is detected by the East, the global variable "Nocutscene" will be true.
For your cutscene script, at the beginning you could have:
if (nocutscene) then {exit} else {goto"ShowtheFilm"}
Or something like that....