What do the 4 digit translations correspond to? User's phones? If so you should just add them as alternate extensions for those users (users can have multiple extensions in seperate partitions assigned to them in Connection if you like - handles overlapping definitions).
If they're just phones that don't correspond to users, yes, you can create contacts - or you can just let users free dial by selecting the option on the call handler(s) in your auto attendant setup that allows users to dial undefined numbers (limited by the system call transfer restriction table of course).
If neither of those is what you're trying to do, let us know...
