A flatfile is required to solve this. You would simply create two columns of data titling one column "cityname" and the other "Mileage"
Populate this with all the cities you will visit. Do not change the city name once it's in place. You can modify the mileage if needed, but once changed, all the references to it will change!
Make sure you sort both the cityname and mileage by the cityname in ascending order.
in a separate sheet, you will type in the cityname in one cell and in another cell you will use a "vlookup" formula. Reference the flat file (cityname info) you have the stored data in. You have to make sure you type in the city name exactly as it is in the flatfile.
Atlanta =vlookup([city], [flatfile],1,)
which will return: