Alright sorry, I thought you were looking for some complex code. Here is a simple example of exactly what you're looking for.
<html>
<head>
</head>
<body>
<script>
function doMath() {
var totalparts = parseInt(document.getElementById('parts_input').value);
var labor = parseInt(document.getElementById('labor_input').value);
var misc = parseInt(document.getElementById('misc_input').value);
var subtotal = totalparts + labor + misc;
var tax = subtotal * .13;
var total = subtotal + tax;
document.getElementById('subtotal_input').value = subtotal;
document.getElementById('tax_input').value = tax;
document.getElementById('total_input').value = total;
}
</script>
<div>Total Parts: <input type="text" id="parts_input" value="1" readonly="true" /></div>
<div>Labor: <input type="text" id="labor_input" onBlur="doMath();" /></div>
<div>Misc: <input type="text" id="misc_input" onBlur="doMath();" /></div>
<div>Sub Total: <input type="text" id="subtotal_input" readonly="true" /></div>
<div>Tax: <input type="text" id="tax_input" readonly="true" /></div>
<div>Total: <input type="text" id="total_input" readonly="true" /></div>
</body>
</html>
Obviously this doesn't grab the dynamic value from a database. If you use PHP you can swap this line:
<div>Total Parts: <input type="text" id="parts_input" value="1" readonly="true" /></div>
for one like this:
<div>Total Parts: <input type="text" id="parts_input" value="<?PHP include('getTotalParts.php'); ?>" readonly="true" /></div>
Where the getTotalParts.php is a file you make to get your database information. It can simply grab the information and do a "echo $totalParts;"
