try this approach:
-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation {
if (startLocation == nil)
{
self.totalDistanceBetween = 0; // declare this variable
self.startLocation = newLocation;
}
CLLocationDistance distanceBetween = [newLocation distanceFromLocation:startLocation ];
startLocation = newLocation;
self.totalDistanceBetween += distanceBetween; // declare this variable
NSString *tripString = [[NSString alloc] //convert to string
initWithFormat:@"%f",
self.totalDistanceBetween];
distance.text = tripString; //update my distance label called distance
}