Making on-screen 'password'

Lokitoes

Hey all,

My friend is trying to make a game where sections within the game can only be accessed via the player entering a password (for example, to change the level or reveal something). I know it is easy to set a rule so that a certain series of keys need to be pressed at the same time, but is there a way to do this so that it is more like entering a password? eg. the keys don't all have to be held down at the same time, but entered in a sequence? Maybe some kind of text box that allows something to occur once a correct sequence is complete?