How to group Extensions

I have a Trixbox 2.5.1 system. It has a TDM400P card with 4 PSTN lines. Can I separate the extensions into two groups, so group 1 can only use pstn line 1&2 to make outbound calls and group 2 can only make outbound call using pstn line 3&4? Thanks.

For some unknown reason this is STILL not a native process in FreePBX. There is a Custom Context module that can be added in to do this. Google for Custom Context and follow the threads. There is a ton of requests, info, etc. on this and still the developers have not built it into the code.