function checkForZero(field) {
	if (field.value == 0 || field.value.length == 0) {
		alert ("This field can't be 0!");
		field.focus();
	} else {
		calculatePayment(field.form);
	}
}

function cmdCalc_Click(form) {
	if (form.price.value == 0 || form.price.value.length == 0) {
		alert ("The Price field can't be 0!");
		form.price.focus();
	} else if (form.ir.value == 0 || form.ir.value.length == 0) {
		alert ("The Interest Rate field can't be 0!");
		form.ir.focus();
	} else if (form.term.value == 0 || form.term.value.length == 0) {
		alert ("The Term field can't be 0!");
		form.term.focus();
	} else {
		calculatePayment(form);
	}
}

function calculatePayment(form) {
	princ = form.price.value - form.dp.value;
	intRate = (form.ir.value/100) / 12;
	months = form.term.value * 12;
	form.pmt.value = Math.floor((princ*intRate)/(1-Math.pow(1+intRate,(-1*months)))*100)/100;
	form.principal.value = princ;
	form.payments.value = months;
}