You are trying to build a taxi or Uber like app.
To determine how far the destination is from the app user, you will probably need to use the Navigate control for an 'exact' distance following roads or calculate a straight line distance between the coordinates of the user at present to his/her destination coordinates either using an algorithm or a routine in the Map component.
Here are some ideas:
and
this discussion might also be helpful to developing you app
or this one