function changeContent (contentId, scriptName, scriptVar, loadingMessage) { 
	var req;

	if (window.XMLHttpRequest) req = new XMLHttpRequest();   
	else if (window.ActiveXObject) {
		try {
			req = new ActiveXObject('Msxml2.XMLHTTP');
		} catch (e){}
		try {
			req = new ActiveXObject('Microsoft.XMLHTTP');
		} catch (e){}
	}
	
	if (scriptName)	{
		if (req) {
			req.onreadystatechange = function () {
				if (req.readyState == 4 && req.status == 200) document.getElementById(contentId).innerHTML = req.responseText;     
			};  
			if (loadingMessage != "") document.getElementById(contentId).innerHTML = loadingMessage;
			req.open("POST", scriptName, true);
			req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
			req.send(scriptVar);
		} 
	} else document.getElementById(contentId).innerHTML = "";
}