function addComparisonItem(item_id){
// added by Ring Tong 2008-08-19
	var noOfAddItems = "";
	//var divName = "DIV_comparison_"+item_id;
	var script  = "block_item_comparison.php?submit=add&item_id="+item_id;
	//var div = document.getElementById(divName);	
	
	ajax.requestFile = script;	
	ajax.onCompletion = function(){
		noOfAddItems = -1;
		//div.innerHTML = "<font color=red>"+ ajax.response +"</font>";
		eval("noOfAddItems = "+ajax.response+";");
		if (noOfAddItems>0){
			alert("This product is added to comparison list!\n\nThere are "+noOfAddItems+" products in your comparison list now.\n(Min. 2 to Compare, Max. 20)");
			document.getElementById("DIV_comparison_"+item_id).style.display = "none";
			document.getElementById("DIV_added_comparison_"+item_id).style.display = "block";
			updateComparisonListBlock();
			location.reload();
		} else {
			alert("NOTE:\nWe allow maximum 20 products in your comparison list, and there are 20 products already.\nTo add more, please remove some products first.");
		}
	}		
	ajax.runAJAX();
}

function updateComparisonListBlock(){
// update block of comparison list (if block exist)
//------------------------------------------------------
		var ajax2 = new sack();
		//alert ("updateComparisonListBlock");
		if (document.getElementById("block_user_comparison_list")){
			//alert ("block exist");
			div = document.getElementById("block_user_comparison_list");		
			//div.innerHTML = "test"; return;
			script  = "block_users_comparison_list_update.php";
			ajax2.requestFile = script;	
			ajax2.onCompletion = function(){
				div.innerHTML = ajax2.response;
			}
			ajax2.runAJAX();		
		}
}