function numeralsOnly(evt) {
	evt = (evt) ? evt : event;
	var charCode = (evt.charCode) ? evt.charCode : ((evt.keyCode) ? evt.keyCode : ((evt.which) ? evt.which : 0));
	if (charCode > 31 && (charCode < 48 || charCode > 57)) {
		alert ("Enter numerals only in this field.");
		return false;
	}
	if (charCode == 13) calculateFields();
	return true;
}

function calculateFields() {
	var refundText='Refund Amount:   $'+insertCommas(Math.round(document.calculator.TMB.value*1.5));
	var monthlyText='Monthly Savings:   $'+insertCommas(Math.round(document.calculator.TMB.value*.2));
	var annualText='Annual Savings:   $'+insertCommas(Math.round(document.calculator.TMB.value*3.9));
	document.calculator.refund.value=refundText;
	document.calculator.monthly.value=monthlyText;
	document.calculator.annual.value=annualText;
	document.getElementById('hiddenFields').style.display='block';
}

function insertCommas(value) {
	var strValue = String(value);
	if (value > 999) {
		strValue = strValue.substr(0,strValue.length-3) + ',' + strValue.substr(strValue.length-3);
	}
	if (value > 999999) {
		strValue = strValue.substr(0,strValue.length-7) + ',' + strValue.substr(strValue.length-7);
	}
	return strValue;
}