Custom Door-and-key GO

[gangstagreen]

What i need to do is make a door, that can only be opened if you have that key. I dont know how to do this, and if you could shed some light on this id be like "omg woot pwn +rep!" For instance i need a church door, called "church door". And i need it to ONLY be opened if you have the "Church Door Key". I really need this :P