function valCheckboxList(sender, e) {
	var sCheckbox = sender.id.substring(sender.id.indexOf("val_") + 4);

	var bChecked = false;

	var aElements = document.getElementById("aspnetForm").elements;
	
	for (var i=0; i < aElements.length;i++) {
		if (aElements[i].id.indexOf(sCheckbox)>0) {
			if (aElements[i].checked) {
				bChecked = true;
			}
		}
	}

	e.IsValid = bChecked;
}