To configure a "call forwarding button" please follow the steps below:

Press the "pause/program" button and then press the "auto dial/store" button.

Next, use the arrow keys to navigate to "FWD/DND all" and press the "auto dial/store" button.

Next, use the arrow keys to navigate to "FWD all:" and start typing the number you wish to forward it to (starting with a 9 for an external number).

Finally, press the "pause/program" button and the button you with to program it to. this will enable that button to be used as a toggle button for call forwarding to the set mobile number.