Ciao a tutti, ho una pagina con questo codice ma non riesco as abilitare e disabilitare le select in base al radio premuto...

<html>
<head>
<SCRIPT LANGUAGE="JavaScript">
<!--
function checkradio1 ()
{
document.form1.S1.disabled=false;
document.form1.S2.disabled=true;
}

function checkradio2 ()
{
document.form1.S1.disabled=true;
document.form1.S2.disabled=false;
}

//-->
</SCRIPT>

</head>
<form name="form1">
<body>
<table><tr>
<td><font face="verdana" size="1"><input type="radio" name="selez" value="A" checked onchange='checkradio1'>AAA</td>
<td><font face="verdana" size="1"><input type="radio" name="selez" value="B" onchange='checkradio2'>BBB</td>
</tr><tr>
<td><select name="S1">
<option selected value="Prova1">Prova1</option>
<option value="Prova2">Prova2</option>
</select>
</td>
<td><select name="S2" disabled>
<option selected value="Prova1">Prova1</option>
<option value="Prova2">Prova2</option>
</select>
</td>
</tr></table>
</body>
</html>