function check_all(formname,elementname) {
	var objelement = document.forms[formname].elements[elementname];
	for (i=0;i<	objelement.length;i++) {
		objelement[i].checked = true;
	}
}

function uncheck_all(formname,elementname) {
	var objelement = document.forms[formname].elements[elementname];
	for (i=0;i<	objelement.length;i++) {
		objelement[i].checked = false;
	}
}