function calculate() {

	var calcPrincipal = document.getElementById('calcPrincipal');
	var calcAnnualRate = document.getElementById('calcAnnualRate');
	var calcNumberOfYears = document.getElementById('calcNumberOfYears');
	var calcMonthlyPayment = document.getElementById('calcMonthlyPayment');
	
	var valueEntered = 0;
	var calcPrincipalGiven = false;
	var calcAnnualRateGiven = false;
	var calcNumberOfYearsGiven = false;
	var calcMonthlyPaymentGiven = false;
	
	
	//alert(calcPrincipal.value + '-' + calcAnnualRate.value + '-' + calcNumberOfYears.value + '-' + calcMonthlyPayment.value);
	
	if ((calcPrincipal != null) && (calcPrincipal.value != null)  && (calcPrincipal.value != '') && (!isNaN(calcPrincipal.value))) {
		valueEntered++;
		calcPrincipalGiven = true;
	}
	if ((calcAnnualRate != null) && (calcAnnualRate.value != null)  && (calcAnnualRate.value != '') && (!isNaN(calcAnnualRate.value))) {
		valueEntered++;
		calcAnnualRateGiven = true;
	}
	if ((calcNumberOfYears != null) && (calcNumberOfYears.value != null)  && (calcNumberOfYears.value != '') && (!isNaN(calcNumberOfYears.value))) {
		valueEntered++;
		calcNumberOfYearsGiven = true;
	}
	if ((calcMonthlyPayment != null) && (calcMonthlyPayment.value != null)  && (calcMonthlyPayment.value != '') && (!isNaN(calcMonthlyPayment.value))) {
		valueEntered++;
		calcMonthlyPaymentGiven = true;
	}
	//alert('Values entered are ' + valueEntered);			
	if(valueEntered < 3) {
		alert('You must specify three NUMERICAL values of the four values of Principal, AnnualRate, Term and Monthly Payment');
	}
	
	alert('example ' + Math.pow(25, 0.5));
	if(!calcPrincipalGiven){
		
	} else if (!calcAnnualRateGiven) {
	
	} else if (!calcNumberOfYears) {
	
	} else if (!calcMonthlyPaymentGiven) {
	}
}



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.principle.value = princ;
    form.payments.value = months;
}