Adding a paging function

Does anyone know if there is a way to essentially add a paging function to an existing system, perhaps via a script? My client owns a business and uses several SONOS speakers tied together as multiple zones playing the same content throughout he store. He wants to be able to play background music (ie: Pandora) but add the functionality of something like pushing a mic button and announcing over the “PA”, then seamlessly returning to the original source. It is possible to add a PORT for the source but that would require one select the alternate “line-in’ source then reselect the original but that's’s less than ideal. A custom scrip that performs these functions would work as the base software lacks (AFAIK) the functionality to do anything but manual switching.  Thanks!