Make a difference between not available and busy


I recently installed freepbx on a Centos PC.

I am loooking for a feature that I can’t find, perhaps one of you can tell me if the thing I want is possible.

When an extension has been chosen, i want a message when the line is busy, and another message when the extension is not available. . As far as I can see, only one option can be checked when the line is not answered.

Do I miss something or am I right???

Thanks in advance for your answer