When you say FRC Dashboard, I'm assuming you're referring to the default LabVIEW dashboard?
You can customize it. I'm personally not familiar with it though. There's should be resources detailing how to customize it if you search around the interwebs. like:
http://forums.usfirst.org/showthread...-See-Your-Data
If you can deal with a textual message in the driver station (not dashboard), take a look at using the
DriverStationLCD class.