Outbound routing based on caller extention?

Hello All!

I am just in a process to migrate our internal asterisk server to Trixbox+FreePBX. What I am trying to do is outbound routing based on who of internal users is calling.

I have internal users:


And I would like them to use different external trunks with different CID like:

100 -> ISDN0, CID 123411
101 -> ISDN0, CID 123412
102 -> ISDN1, CID 123413

I guest I have to do that manually in asterisk config files. But how can I override FreePBX config?

Best regards