Is there a CAN message for sending text to MFD?

When certain actions happen, like the temp dropping to 37, or changing the temperature value, or something like that what tells the bar that drops down on the MFD and displays a message what to show?

Meaning, does a message in ASCII format (yeah right but how cool would that be) get sent to the MFD along with a "show msg" command and the MFD figure out what to overlay? Or does the MFD get the signal that the temp changed then queries the data itself and displays it itself? Or does all this happen in some ECU and then get sent as video data to the MFD?

My main reason for asking is wanting to inject alert-type messages onto the MFD keeping the OEM look/feel/integration.

Does anyone know?