I've been trying to do updates of kml through a network link without success.
Here is an example from the KML 2.1 tutorial.
Load the following file (Point-load.kml) into AGX:
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.1">
<NetworkLink>
<name>Loads Point.kml</name>
<Link>
<href>http://code.google.com/apis/kml/documentation/Point.kml</href>
</Link>
</NetworkLink>
</kml>
This should create two placemarks.
Then load the following file (Update-load.kml):
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.1">
<NetworkLink>
<name>Update</name>
<Link>
<href>http://code.google.com/apis/kml/documentation/NetworkLinkControl-Update.kml</href>
</Link>
</NetworkLink>
</kml>
This should update one of the Placemarks to a different name and does in Google Earth, but doesn't seem to work in ArcGIS Explorer.