There is no “simple” way to do this, it will require coding…
You can use the wix-realtime API. As stated in the documentation:
Using the Realtime API you can create channels and channel resources where messages can be published. Site visitors who subscribe to a channel receive the messages published to that channel. When a message is received you can handle the message any way you choose, such as displaying the contents of the message or changing the state of page elements depending on the contents of the message. You can also manage the permissions of who can read from specific channels.
You can create a channel for your “on air now” messages, and then display or hide the on air now text on the screen.
Perhaps you can hire a Wix Velo Expert to do this for you.