function datechange(grpName, formId, allowNulls) {
	var extraDayForNull = 0;
	
	if (allowNulls) extraDayForNull = 1;
	
	var xForm = document.getElementById(formId);
	var inpDay = xForm.elements[grpName + '_1'];
	var inpMth = xForm.elements[grpName + '_2'];
	var inpYr = xForm.elements[grpName + '_3'];
	var iCurrentDaySelected = inpDay.value;
	var iDayInMonth = DaysInMonth(inpMth.value - 1,inpYr.value) + extraDayForNull;
	
	var iCurrentDaysInMonth = inpDay.options.length + extraDayForNull;
	
	if (allowNulls) iCurrentDaysInMonth++;
	
	if (iCurrentDaysInMonth > iDayInMonth) {
		inpDay.options.length = iDayInMonth;
		if (iCurrentDaySelected > iDayInMonth) inpDay.selectedIndex = inpDay.options.length - 1;
	}
	
	while (iCurrentDaysInMonth < iDayInMonth) {
		iCurrentDaysInMonth++;
		inpDay.options[inpDay.options.length] = new Option(iCurrentDaysInMonth,iCurrentDaysInMonth);
	}
}

function DaysInMonth(xMon,xYear) {
	var firstofthisMonth = new Date();
	firstofthisMonth.setFullYear(xYear,xMon,32);
	firstofthisMonth.setMonth(firstofthisMonth.getMonth(),0);
	return firstofthisMonth.getDate();
}