Hola
Veamos si esto lo que quieres
Código javascript
:
Ver original<script type="text/javascript">
function Block(esto,id) {
if(esto==2) {
document.getElementById(id).disabled=true;
}else{
document.getElementById(id).disabled=false;
}
}
</script>
</head>
<body>
<select id="lista" onchange="Block(document.getElementById(this.id).options[document.getElementById(this.id).selectedIndex].value, 'Aukera');">
<option value="1">Uno</option>
<option value="2">Dos</option>
</select>
<select id="Aukera">
<option value="1">Uno</option>
<option value="2">Dos</option>
</select>
Suerte