That would work but you cant let the player know which key very easily, let me "borrow" Land of Shadows resource pack
*looks through
Got it! ok, that part of the event should look like this
Show Picture: (#), (name), upper left, (0,0) (100%, 100%), 255, Normal
Change Text Options: Bottom, Hide
Text: .
Erase Picture: (#)
Change Text Options: Bottom, Show
If you don't understand just ask