There are 2 RMP radio management panels on the pedestal, those panels you normally tune vhf com freq.
The bottom line of switches are marked standby, it is i tended for a backup metod to tune nav frequenzes in case both mcdu's are faulty.
If the left button(nav) below the plastic guard is pushed, then one of the other buttons can be selected(vor, ils, ndb).
Lets say vor is selected, a vor freq can be dialed in the stby window(where normally you dial a com freq), then push transfer and the freq is transferred to the actice window. Then a C (for course) appears in the stby window and you can dial in the vor course
This might be very complicated to make it work, so i dont expect you to implement this soon :p
Thanks