Forward main number calls to an external number from a desk phone and app on demand

We have smaller office and when everyone leaves for lunch, we would like to forward the main number to a calling service we pay for. Presently, we can do this by dialing #72 and then the number and when we get back, we dial #73 to unforward them. This option is not available at RingCentral. We are using Polycom phones, and someone suggested an on demand forward button, presently I'm asking for such a button to be created for us. But, it would be nice to be able to do it with a keycode and that way other physical phones or the RingCentral app can take advantage of this function.