well I dont have access to my computer to testrun your program on the account that it is broken
but from the sneak peak at your data file, I'd say that you're just just displaying a list of precalculated distances... that's not the way it should be
It is not that much harder load locations of the cities and find the distance between the two points Math.Distance
would be much easier to add another city as well since you would not have to calculate the distance to every other city yourself and edit the datafile. + giving the user an option to enter the GPS coordinates of the city to add it to the map would be a nice feature