Perhaps expand on your requirements, and clarify what sort of signal/message you want to send.
Something like this
https://4js.com/online_documentation/fjs-fgl-manual-html/#c_fgl_ClassMessageServer.html maybe close.
The difficulty with most of these types of requests is having to have something in every dialog statement in order to respond to the notification no matter what dialog you are in and/or do you want to respond to the signal/message straight away or can it wait until the user finishes what they are doing.