How do I get a functional KML file to display on GoogleMap API v3

The available GoogleMaps javascript samples do not allow me to display a KML file as a selectable controlled by checkbox selection.  Also is it possible to use relative paths instead of urls.

<?xml version="1.0" encoding="UTF-8"?> 
<kml xmlns="http://earth.google.com/kml/2.0"> <Document>
<Placemark> 
<name>MGAZ54</name>
 <Polygon>   
 <altitudeMode>absolute</altitudeMode>
  <outerBoundaryIs>  <LinearRing>
  <coordinates>
   138, -28, 0. 
   144, -28, 0.
   144, -38.5, 5000.
   138, -38.5, 10000.
  </coordinates>
 </LinearRing> </outerBoundaryIs> </Polygon>
 <Style> 
  <PolyStyle>  
   <color>#000</color>
  <outline>1</outline>
  </PolyStyle> 
 </Style>
</Placemark>
<Placemark> 
<name>MGAZ55</name>
 <Polygon>   
 <altitudeMode>absolute</altitudeMode>
  <outerBoundaryIs>  <LinearRing>
  <coordinates>
   144, -28, 0. 
   150, -28, 0.
   150, -38.5, 5000.
   144, -38.5, 10000.
  </coordinates>
 </LinearRing> </outerBoundaryIs> </Polygon>
 <Style> 
  <PolyStyle>  
   <color>#000</color>
  <outline>1</outline>
  </PolyStyle> 
 </Style>
</Placemark> 
<Placemark> 
<name>MGAZ56</name>
 <Polygon>   
 <altitudeMode>absolute</altitudeMode>
  <outerBoundaryIs>  <LinearRing>
  <coordinates>
   150, -28, 0. 
   156, -28, 0.
   156, -38.5, 5000.
   150, -38.5, 10000.
  </coordinates>
 </LinearRing> </outerBoundaryIs> </Polygon>
 <Style> 
  <PolyStyle>  
   <color>#000</color>
  <outline>1</outline>
  </PolyStyle> 
 </Style>
</Placemark> 
</Document> 
</kml>

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