There are a few ways to do that... (its been a while, so this might have slightly wrong function names or something)
a] make a special door script that checks to see if an entity is around (checking to see if you can get the entity when its inside a node is a decent way of checking if its alive, if the entity in question has a unique name you can just see if you can getEntity("UniqueName") or not
b] make a node script that has access to the door and the entity, and the node is set up in such a way that it will catch the entity if its alive, inside its box
-- at top
done = false;
-- in start up
door = node_getNearestEntity(me, "Door");
-- in update
if ~done and node_getEntityInside(me, "BobTheEnemy") == 0 then
-- entity is dead
entity_setState(door, STATE_OPEN);
done = true;
end
