Send an event to all rooms from lobby

Hi,
I want to be able to trigger an action from the lobby to all rooms but I don't know how to di it.

I tried to make it using a workaround: customproperties. That way I can list all rooms in the lobby and "see" the custom properties on each room and if they change, but It seems I can't change any custom property from the lobby (it's only readonly) to be able to detect that change "inside" the room (that way I could trigger an action from inside the room when the change in the custom properties are detected)

Is there any kind of "event" or "signal" that can be sent to all rooms (some sort of general RPC).

The point of all this is to start an event (fire some music and animations) in all multiplayer rooms at an specific time. I want to do it from lobby and monitor if all works fine by looking at the changes in customproperties I can make from inside the room (for example, in case something goes wrong I just can change a specific custom property and detect it for "outside" in the lobby just listing all rooms and its properties).

Any idea?