I understand slightly, your missing the point of it passing the incoming callee's number, That way no matter who calls, it'll always ring my cell using their number.I do this: ( I have 14 numbers so I have to )
A call comes in - no one in the office -> Voicemail says to press 1 (follow Me) FollowMe Takes over.
in the number(s) to call is the Extension (so it rings again) and my Cell Number with a dial prefix (e.g. 612075551212#)
Now the system looks in your outgoing Routes for this prefix and uses this to place the call -- in the outbound route is an option Override Extension CID or Force Route CID (film ran out of my photographic memory ) now place in the trunks you want the call to go out in the list, submit, and apply changes.
In Trunks is the same type option of Force Trunk CID so you can set it here too but if you want to try different trunks, its best to use the Outbound route method.
When a call comes to my Cell phone the CID is the number the person called (2075551210 may be my Notary Business where as 2075558787 may be one of my amateur radio clubs I run the PBX for. In this way I have the group name in my contacts so when I answer - I answer for the group they called.
If you need some help, in my profile is my "Main" website and on there a contact us page with a phone number. Call it and ask for 1-Zed-01 (I do not respond to names - those calls get sent to Lenny ), and I will help you through setting one up.