OK this isn't a cheat but it's a tip for all of you who need to do the Ultimate Heist (last mission for thieves guild).
When you are in the temple that you have to sneak past the gaurds and monks, don't get caught.
It will tell you to escape but you don't want that until you have the scroll.
If you do get caught do not try to escape because you will not be able to get back in.
So basically just take your sweet time and find the scroll without the marker.