function createRequestObject() {
    var tmpXmlHttpObject;
    
    //depending on what the browser supports, use the right way to create the XMLHttpRequest object
    if (window.XMLHttpRequest) { 
        // Mozilla, Safari would use this method ...
        tmpXmlHttpObject = new XMLHttpRequest();
	
    } else if (window.ActiveXObject) { 
        // IE would use this method ...
        tmpXmlHttpObject = new ActiveXObject("Microsoft.XMLHTTP");
    }
    
    return tmpXmlHttpObject;
}

function getListClass(no){//USED
	var id_course = document.getElementById('Course_select_'+no).options[document.getElementById('Course_select_'+no).selectedIndex].value;
	var	data = "id_course="+id_course+"&no="+no;
	var http = createRequestObject();
    http.open('POST',"ajax/getClassList.php",true);

    http.onreadystatechange = function(){
	
	    if(http.readyState == 4){
	        var response = http.responseText;
	        document.getElementById('select_container_'+no).innerHTML = response;
	    }
    };
  	http.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
	http.send(data);
    
}