function setElementVisible(item_name) {
	var aantal_items = document.getElementById("aantal_submenu_items").innerHTML;
	for(var i = 0; i < aantal_items; i++) {
		var item_name_temp = "submenu_"+i;
		document.getElementById(item_name_temp).style.display = "none";
	}
	document.getElementById(item_name).style.display = "block";
}