function kalender(datum, select, data){
		var xmlhttp = xmlhttp_instance();
		xmlhttp.open("GET", "kalender.php?datum="+datum+"&select="+select+"&data="+data);
		xmlhttp.onreadystatechange=function() {
			if (xmlhttp.readyState==4){
				document.getElementById('cal').innerHTML = xmlhttp.responseText;
			}
		}
		xmlhttp.send(null);
	}

	function xmlhttp_instance(){
		var xmlhttp=false;
		/*@cc_on @*/
		/*@if (@_jscript_version >= 5)
		// JScript gives us Conditional compilation, we can cope with old IE versions.
		// and security blocked creation of the objects.
		 try {
		  xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
		 } catch (e) {
		  try {
		   xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
		  } catch (E) {
		   xmlhttp = false;
		  }
		 }
		@end @*/
		if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
		  xmlhttp = new XMLHttpRequest();
		}

		return xmlhttp;
	}