You can create a text file in the flash memory on the cRIO that says which robot it is. Then have the program open the file. An easier way might be to use the Preferences class and set it up once, then each time you start up check the preference settings.
This page shows how to use the Preferences with the Dashboard for setting the values which are stored on the robot. You can do that once for each robot then have your program read them at startup.
http://wpilib.screenstepslive.com/s/...smartdashboard