ROVERQTH but there are several methods available listed below.

John, K3CT

http://n1mm.hamdocs.com/tiki-index.php?page=Setup+QSO+Parties+-+CW+and+SSB&structure=N1MM+Logger+Documentation#Rover_Mobile_and_County_Line_Support

The operating location or RoverQTH can be set:

• in the Station Data window, RoverQTH box. This box will automatically update when you use any of the other methods of setting RoverQTH below.
• by right clicking on the county or grid in the Multiplier window and selecting "Set RoverQTH"
• by typing CTRL+H
• or by typing ROVERQTH in the Entry Window callsign box and pressing Enter. This opens a window to input the county designator, typically 3 or 4 characters.