Targeting an outbound route based on extension

I have built my individual PSTN lines such that dial ‘9’ grabs trunk 1, dial ‘8’ grabs trunk 2, dial ‘7’ grabs trunk 3…

There’s no way I can tell my user base that they’re gonna have to dial ‘7’ to get out from department X, and dial ‘8’ to get out if you’re in the department Y.

I’d like to force the call to the appropriate route based on from which extension the outbound call originates. Exts 100 - 108 dial ‘9’ calls go over outbound route 8, and exts 109 - 112 dial ‘9’ calls go out over route 7.

Any thoughts on how to acheive this?.. Anyone?..

Thank Y’all!

Use contexts, take a look on the book asterisk the definitive guide. Use google its free and online. If my english dont lie to me thats very basic stuff.