Help needed with custom context

Hi Everyone,
I need to force some extesions to use another trunk.(different companys Now I now it can be done with custom context, but I installed it and dont understand it …
Can you guys help me out how to do it ?
I`m using Freepbx 2.10

You can avoid custom contexts by setting up outbound routes and putting the CID of the extension to use that route in the dial pattern CID field.

Thanks, I will give it a try
Regards ,

This is what I did :

thats the right way ?
Regards Harry