/** AJAX class
  * holds an instance of XMLHttpRequest
  *
  * creates an XMLHttpRequest instance
 */
function createXmlHttpRequestObject() {
	// will store the reference to the XMLHttpRequest object
	var xmlHttp;
	// this should work for all browsers except IE6 and older
	try {
		// try to create XMLHttpRequest object
		xmlHttp = new XMLHttpRequest();
	}
	catch(e) {
		// assume IE6 or older
		var XmlHttpVersions = new Array("MSXML2.XMLHTTP.6.0",
		"MSXML2.XMLHTTP.5.0",
		"MSXML2.XMLHTTP.4.0",
		"MSXML2.XMLHTTP.3.0",
		"MSXML2.XMLHTTP",
		"Microsoft.XMLHTTP");
		// try every prog id until one works
		for (var i=0; i<XmlHttpVersions.length && !xmlHttp; i++) {
			try {
				// try to create XMLHttpRequest object
				xmlHttp = new ActiveXObject(XmlHttpVersions[i]);
			}
			catch (e) {}
		}
	}
	// return the created object or display an error message
	if (!xmlHttp) alert("Error creating the XMLHttpRequest object.");
	else return xmlHttp;
}

/**
 * Check if asynchronous call is in progress
 *
 * @param XMLHttpRequest xhro
 * @return boolean
 */
function is_call_in_progress(xhro) {
	var status = xhro.readyState;
	if (status == 4 || status == 0)
		return false;
	
	return true; //1, 2, 3
}