I'm not sure I follow completely. If you carb your keg at say 37°F to 11 PSI (which would get you around 2.5 vols), then let it free rise to room temp (disconnected from the gas), you'll find that the pressure will eventually equilibriate to the correct psi for 2.5 vols at whatever that temp is (which would be around 30psi for a 67°F room).
In other words, when you get to your destination and hook up the keg to the jockey box, you'd hook the gas up to the keg according to the CO2 chart for the temp it is at and the vols you originally carbed to. In the example above, you'd have the gas set to about 30 psi. The only way you'd need to adjust the pressure is if the temp swings more than 5 degrees in either direction for an extended period.
Just as a side note in case I'm not being clear, if you originally carb a keg to 2.5 vols and then disconnect the gas, the beer will always stay carbed at that level, regardless of the temperature. The pressure in the keg will increase with the temperature, but the carbination level will remain constant. 11PSI @ 37°F === 30PSI @ 67°F === 2.5 vols. As long as you know your ambient temperature and your beer's carbination level, you can look at the chart to determine the PSI to set the gas to to ensure the beer stays properly carbed while serving.