Rieccomi

codice:
<script type="text/javascript">
function controllaSomma() {
a = (document.getElementById('a').value)-0;
b = (document.getElementById('b').value)-0;
c = (document.getElementById('c').value)-0;
d = (document.getElementById('d').value)-0;
e = (document.getElementById('e').value)-0;
somma = a+b+c+d+e;
if (somma > 10) {
window.alert("Attenzione! La somma totale deve essere al massimo 10!");
document.getElementById('invia').disabled = true;
}
else {
document.getElementById('invia').disabled = false;
}
document.getElementById('sommaparz').innerHTML = "Somma: "+somma;
}
</script>

<form id="form1" name="form1" method="post" action="">
<label>
<select name="a" id="a" onChange="controllaSomma();">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
</label>
<select name="b" id="b" onChange="controllaSomma();">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
<select name="c" id="c" onChange="controllaSomma();">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
<select name="d" id="d" onChange="controllaSomma();">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
<select name="e" id="e" onChange="controllaSomma();">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
il valore totale non deve superare 10
<div id="sommaparz">Somma: 5</div>
<input type="submit" value="Ok" id="invia">
</form>
Ciao