function calculateData(input,calculator_form){
	if(input.value==''){
		input.value=input.defaultValue
	}
    
	            status=''
                msg ="This field requires numbers only: " + input.value;
                var str = input.value;
				if (str.indexOf(",") > 0 ) {
					var str2 = str.substring(0,(str.indexOf(","))) + str.substring((str.indexOf(",")+1), str.length);
					input.value= str2;
				}
            
			    str = input.value;
                for (var i = 0; i < str.length; i++){
                                var ch = str.substring(i, i + 1)
                                
								if ((ch < "0" || "9" < ch) && ( ch != '.')  && (ch != '-')){
                                	input.focus()
                                	input.value=input.defaultValue;
                                	input.select()
                                	status=msg;
                                } 
        		}
        add_data(calculator_form)
 }

function add_data(calculator_form){
	var total1,total2,total3,total4,total5,total6;


        if (calculator_form.interest_rate.value == 0) {calculator_form.interest_rate.value=9}
        if (calculator_form.no_of_payments.value == 0) {calculator_form.no_of_payments.value=1}

        total1=((calculator_form.cost1.value*1)+(calculator_form.destination.value*1))              

        total2=(total1*1-calculator_form.trade_in.value*1)
        if (total2 < 0) { total2=0 }

        total3=((total2*(calculator_form.sales_tax.value*'.01'))+total2*1)
        if (total3 < 0) { total3=0 }

        total4=(total3*1-calculator_form.incentives.value*1)
        if (total4 < 0) { total4=0 }

        total5=(total4*1-calculator_form.down_payment.value*1)
        total6=(total5*1)
        if (total6 < 0) { total6=0 }

        calculator_form.total_cost.value=((total6*1))
        compute_data(calculator_form)
}




function compute_data(calculator_form)
{
    var i = calculator_form.interest_rate.value;
	if (i > 0.0) {
        i = i / 100.0;
        }
    i /= 12;
    var pow = 1;
    for (var j = 0; j < calculator_form.no_of_payments.value; j++)
        pow = pow * (1 + i);
	var x = (calculator_form.total_cost.value * pow * i) / (pow - 1);
	x = Math.round(x);
	calculator_form.monthly_payments.value = x
}
function selectField(field)
{
        field.select()
}
function resetForm(calculator_form)
{
        calculator_form.cost1.value = "0"
        calculator_form.destination.value="0"
        calculator_form.trade_in.value="0"
        calculator_form.incentives.value = "0"
        calculator_form.down_payment.value = "0"
        calculator_form.total_cost.value="0"
        calculator_form.interest_rate.value="6.5"
        calculator_form.no_of_payments.value="48"
        calculator_form.monthly_payments.value="0"
}