function get_progress(tracking_number) {
  var xmlobj;

  try {
    xmlobj = new XMLHttpRequest();

  } catch (e) {
    try {
      xmlobj = new ActiveXObject("Msxml2.XMLHTTP");

    } catch (e) {
      try {
        xmlobj = new ActiveXObject("Microsoft.XMLHTTP");

      } catch (e) {
        alert("Your browser does not support the required functionality to use this feature.");
        return;
      }
    }
  }

  xmlobj.onreadystatechange=function() {
    if (xmlobj.readyState == 4) {
      current_progress = eval("(" + xmlobj.responseText + ")");
      
      begin_plot(true);
      
    }
    
  }

  xmlobj.open('GET', "?mode=ajax&number=" + tracking_number, true);
  xmlobj.setRequestHeader('Connection', 'close');
  xmlobj.send(null);
  
}