George, that seems cumbersome. Don't you have a menu page with a GPS tripmeter on it that records distances? Not sure about the C80 but Garmin has one, it's resettable for each trip and will record totals until you reset that. I would think there's one there somewhere...I usually transfer that info to a paper logbook after each significant trip, along with engine hours, weather observations, etc. On the Garmin, you can do trip planning too, if you have fuel consumption curve info, it'll keep track of things like that too, based on speed being traveled.
Looked for the manual on the website to check myself but, if it's there for the C80, it's well hidden..
We're headed for DownEast Maine this weekend, still got this snowbird thing backwards!!
Charlie