Help - Direct Number

I implemented an asterisk PBX for our main office, but i have one question.
I’m using the IP phones from Linksys (SPA941), configured with two lines. One is the internal extension and the other is the direct line for each person. Im using an PRI E1 trunk and i managed to route the incoming calls for each person’s direct number to their direct line.
Now, each person can select an direct outside line by dialing 9 in front of the number.
I defined a trunk for each person direct line.
The problem i have is: How do i make the outgoing call from the person direct line to go through his specific trunk, without dialing 9 or anything else in front of the number?
In other words how can i make asterisk select the trunk based on the extension number that is initiating the call?
Sorry for my english.
Thank you

I think you’re adding too much complexity…

There is no need to “dial through specific trunk”. As soon as you have E1 with the group of numbers assigned to it you just need to properly set the CallerID information on the outgoing call.

Ok, but how can i use other outgoing dial plan for some extensions?
On the extensions bound to the direct number i don’t want to dial 9 to select a line.
I wanted to use different trunks because i want to reserve some channels for the conference rooms, and with 9 they can take a channel from the 5 channels that i assigned to the operator, and also when they press the button for the direct line from their phone i want them to be able to dial the number directly without 9.