codice:
<script>
function CalcolaLicenze(qt){
var pz = (qt < 4) ? 350 : 250;
document.getElementById('licenze').value=(qt*pz);
}
</script>
<select id="sss" size="1" name="licenze" onChange="CalcolaLicenze(this.options[this.selectedIndex].value)">
<option selected value=1>1</option>
<option value=2> 2</option>
<option value=3> 3</option>
</select>