SeGun,
<!DOCTYPE HTML>
<html>
<head>
<title></title>
<meta charset="utf-8" />
</head>
<body>
<select>
<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>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
<option value="11">11</option>
<option value="12">12</option>
</select>
<select>
<option value="0">0</option>
<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>
<option value="6">6</option>
<option value="7">7</option>
<option value="8">8</option>
<option value="9">9</option>
<option value="10">10</option>
<option value="11">11</option>
</select>
<script>
var select = document.getElementsByTagName('select')[0];
select.addEventListener('change', function() {
var i = this.selectedIndex
var select = document.getElementsByTagName('select')[1];
select.options.length=0
for (var k=0; k<12-i; k++) {
select.options[k] = new Option(k, k);
}
});
</script>
</body>
</html>