Calling number when forwarding call...

snickered

When I use the "CFwdAll" button on my 7960 phone it sends the calling number as the person that called. Is there a way to send the calling number as the extension of my 7960? So, as an example:

I use "CFwdAll" on my 7960 phone which has button 1:1 (number 5001) to forward the call to my cell phone which is 555.555.5555. Now, an outside person calls and my cell phone displays their number, rather than my 7960's number which is 5001.

Is it possible to set the calling number as 5001?