title: Display a hierarchy of placemarks in google earth
body: <p>I am trying to use kml to implement a heirarchy of regions as describe in
  <a href="http://code.google.com/apis/kml/documentation/kml_21tutorial.html#regionbasednl" rel="nofollow">KML 2.1 Tutorial</a></p>
  
  <p>I would like to have a feature(polygon or icon) representing a region and when the region becomes active I would like to display a feature representing each of the regions immediate children but no longer display the icon representing the parent region.</p>
  
  <p>An example would be if I had a region representing Canada and a placemark in the middle of the region. When the Canada region becomes active I want the canada placemark to disappear and want to display placemarks over the provinces of Canada(a region and placemark for BC, Alberta ect.).  Then when the BC region became active I would like to replace the bc placemark with placemarks for cities in bc.</p>
  
  <p>Any help would be greatly appreciated.
  Thank you.</p>