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 (Ext.fly('me_price').dom.value == 0 || Ext.fly('me_price').dom.value == 0) {
		alert ("The Price field can't be 0!");
		Ext.fly('me_price').dom.focus();
	}
	else if (Ext.fly('me_ir').dom.value == 0 || Ext.fly('me_ir').dom.value == 0) {
		alert ("The Interest Rate field can't be 0!");
		Ext.fly('me_ir').dom.focus();
	}
	else if (Ext.fly('me_term').dom.value == 0 || Ext.fly('me_term').dom.value.length == 0)
	{
		alert ("The Term field can't be 0!");
		Ext.fly('me_term').dom.focus();
	}
	else
	{
		calculatePayment(form);
	}
}

function calculatePayment(form)
{
    princ = Ext.fly('me_price').dom.value - Ext.fly('me_dp').dom.value;
    intRate = (Ext.fly('me_ir').dom.value/100) / 12;
    months = Ext.fly('me_term').dom.value * 12;
    Ext.fly('me_pmt').dom.value = Math.floor((princ*intRate)/(1-Math.pow(1+intRate,(-1*months)))*100)/100;
  	Ext.fly('me_principle').dom.value = princ;
		Ext.fly('me_payments').dom.value = months;
		
}