Setup call forward if not available in FreePBX

[Richard \(Rogers @ work\)]

Hi All,

I am trying to a feature called "call forward/redirect" (offered by
Bell) when unavailable in my FreePBX. (Trixbox 1.2) 

This is a simple feature which after so many incoming rings, it assumes
no one is available and then automatically forward to another number.

Any suggestion is appreciated.

Thanks,
Richard