Custom Extension and Destinations
This is a how-to approach using FreePBX 2.10

If this is your first look at custom destinations, you're not a guru, and you're not familiar with goto statements, you need to know some basic facts.

1. Admin > Custom Destinations will create a name for your custom context and make the context available as a menu choice in the Applications > Follow Me menu.
2. You need to manually add your new custom context into /etc/asterisk/extensions_custom.conf

See /etc/asterisk/extensions_custom.conf.sample for some ideas on how your new context might look.

Here's an example of how we utilize an external asterisk-based voicemail system using a custom destination:

Here are a couple of good writeups on using custom destination:

http://ronaldgibson.googlepages.com/unknowndestinationfreepbxv2.4.0beta

http://mbrevda.blogspot.com/2008/10/miscellaneouscustom-applicationextensio.html