XML onLoad only runs once

Hi. I was wondering if anyone has had the same problem.
I start my frame by creating an XML object and declaring its onLoad function as follows:

var myXML:XML;
myXML=new XML();


Some time later on. I wish to reload the XML object with a different XML file or the same XML file but the onLoad function only runs once! I tried just using a myXML.load call as well as deleting the object, creating a new XML object and loading a new file but none of this works. Any suggestions as to how to tackle this problem?