chart1.setDataURL(escape("xmlfile.xml?currTime=" + getTimeForURL()));
/**
  * getTimeForURL method returns the current time
  * in a URL friendly format, so that it can be appended to
  * dataURL for effective non-caching.
 */
 function getTimeForURL(){
  var dt = new Date();
  var strOutput = "";
  strOutput = dt.getHours() + "_" + dt.getMinutes() + "_" + dt.getSeconds() + "_" + dt.getMilliseconds();
  return strOutput;
 }