// Original JavaScript code by Chirp Internet: www.chirp.com.au
  // Please acknowledge use of this code by including this header.

  var req;

  function loadXMLDoc(url, params)
  {
    if(window.XMLHttpRequest) {
      try {
        req = new XMLHttpRequest();
      } catch(e) {
        req = false;
      }
    } else if(window.ActiveXObject) {
      try {
        req = new ActiveXObject("Msxml2.XMLHTTP");
      } catch(e) {
        try {
          req = new ActiveXObject("Microsoft.XMLHTTP");
        } catch(e) {
          req = false;
        }
      }
    }
    if(req) {
      req.onreadystatechange = processReqChange;
      req.open("GET", url + '?' + params, true);
      req.send(null);
      return true;
    }
    return false;
  }

  function getNodeValue(parent, tagName)
  {
    var node = parent.getElementsByTagName(tagName)[0];
    return (node && node.firstChild) ? node.firstChild.nodeValue : false;
  }

  function processReqChange() 
  {
    if(req.readyState == 4 && req.status == 200) {
      var response  = req.responseXML.documentElement;
      var commands = response.getElementsByTagName('command');
      for(var i=0; i < commands.length; i++) {
        method = commands[i].getAttribute('method');
        switch(method) {
          case 'alert':
            var message = getNodeValue(commands[i], 'message');
            window.alert(message);
            break;
          case 'setvalue':
            var target = getNodeValue(commands[i], 'target');
            var value = getNodeValue(commands[i], 'value');
            if(target && value) {
              document.getElementById(target).value = value;
            }
            break;
          case 'setdefault':
            var target = getNodeValue(commands[i], 'target');
            if(target) {
              document.getElementById(target).value = document.getElementById(target).defaultValue;
            }
            break;
          case 'focus':
            var target = getNodeValue(commands[i], 'target');
            if(target) {
              document.getElementById(target).focus();
            }
            break;
          case 'setcontent':
            var target = getNodeValue(commands[i], 'target');
            var content = getNodeValue(commands[i], 'content');
            if(target && content) {
              document.getElementById(target).innerHTML = content;
            }
            break;
          case 'setstyle':
            var target = getNodeValue(commands[i], 'target');
            var property = getNodeValue(commands[i], 'property');
            var value = getNodeValue(commands[i], 'value');
            if(target && property && value) {
              document.getElementById(target).style[property] = value;
            }
            break;
          case 'setproperty':
            var target = getNodeValue(commands[i], 'target');
            var property = getNodeValue(commands[i], 'property');
            var value = getNodeValue(commands[i], 'value');
            if(value == "true") value = true;
            if(value == "false") value = false;
            if(target) {
              document.getElementById(target)[property] = value;
            }
            break;
          default:
            window.console.log("Error: unrecognised method '" + method + "' in processReqChange()");
        }
      }
    }
  }