I use a PDA style system. go to a combo keypad door, transfers player to a map made to look like a number pad w/ other background. then changed character picture cursor to a arrow style cross hair and changed number pad to light up when pressed. basically works like; player goes to a door, which turns into number a pad/handle/door. then pushes a button to show animation of dusting buttons to show which ones have been pushed. then pda pops up, number pad is used to guess combination. It's all events, fairly simple and runs pretty well. it works great if you're doing a game where you're breaking into a commercial building or modern house. And the system doubles for multiple devices