Hola, famp.
Pureba esto:
Código PHP:
<html>
<head>
<script>
function calcular() {
ne=eval(document.getElementById('neto').value);
iv=eval(document.getElementById('iva').value);
tiv = ne * iv /100;
tot = ne + tiv;
document.getElementById('totiva').value=tiv;
document.getElementById('total').value=tot;
}
</script>
</head>
<body>
<input type="text" id="neto" value="0" onkeyup="calcular()" />
<input type="text" id="iva" value="0" onkeyup="calcular()" />
<input type="text" id="totiva" disabled="disabled" />
<input type="text" id="total" disabled="disabled" />
</body>
</html>
Saludos,
