Sumar valores de combobox

[_cronos2]

Código Javascript:

function calcular(){
var totalOrigen = parseInt(document.form1.origen.options[document.form1.origen.selectedIndex].value);
var totalDestino = parseInt(document.form1.destino.options[document.form1.destino.selectedIndex].value);
document.form1.textfield.value = totalOrigen + totalDestino;
}
 

Código HTML:

<form id="form1" name="form1" method="post" action="">
<p>
<select name="origen">
<option value='0'>Elija Origen...</option>
<option value='1'>Granada</option>
</select>
<select name="destino">
<option value='0'>Elija Destino...</option>
<option value='100'>M&aacute;laga</option>
<option value='44'>Aeropuerto</option>
</select>
</label>
</p>
<p>
<label>
<input name="button" type="button" value="Calcular" onclick="calcular()">
</label>
<label>
<input type="text" name="textfield">
</label>
</p>
</form>
 

Saludos (: