function check_dates(f){
	if(!f.datefrom.value){
		alert("Please enter at least a from date");
		f.datefrom.focus();
		return false;
	}
	if(!f.events.checked && !f.courses.checked){
		alert("Please select either events or courses or both");
		f.datefrom.focus();
		return false;
	}
	return true;
}