Hola de nuevo V_G.
Prueba esto:
Código PHP:
<html>
<head>
<script language="JavaScript">
var aCks1 = new Array("Primera", "Segunda", "Tercera");
var aCks2 = new Array("Una", "Otra");
var aCks3 = new Array("Check-1", "Check-2", "Check-3", "Check-4", "Check-5", "Check-6");
var aCks4 = new Array("Check-1", "Check-2", "Check-3", "Check-4", "Check-5", "Check-6");
var aCks5 = new Array("Check-1", "Check-2", "Check-3", "Check-4", "Check-5", "Check-6");
var aCks6 = new Array("Esta sola");
function cambia(oSel){
var nChecks;
var nSel = oSel[oSel.selectedIndex].value;
for (var i = 0; i < 6; i++){
eval("document.frm.ck" + String(i + 1) + ".style.display = 'none'");
eval("document.getElementById('sp' + String(i + 1)).innerHTML = ''");
}
eval("nChecks = aCks" + String(nSel) + ".length");
for (var i = 0; i < nChecks; i++){
eval("document.frm.ck" + String(i + 1) + ".style.display = ''");
eval("document.getElementById('sp' + String(i + 1)).innerHTML = aCks" + String(nSel) + "[i]");
}
}
</script>
</head>
<body>
<form name="frm">
Opción
<select name="NumeroDeChecks" onchange="cambia(this)">
<option value="0"></option>
<option value="1">Opcion 1</option>
<option value="2">Opcion 2</option>
<option value="3">Opcion 3</option>
<option value="4">Opcion 4</option>
<option value="5">Opcion 5</option>
<option value="6">Opcion 6</option>
</select><br>
<table>
<tr>
<td>
<input type="checkbox" name="ck1">
</td>
<td id="sp1">
Uno
</td>
</tr>
<tr>
<td>
<input type="checkbox" name="ck2">
</td>
<td id="sp2">
Dos
</td>
</tr>
<tr>
<td>
<input type="checkbox" name="ck3">
</td>
<td id="sp3">
Tres
</td>
</tr>
<tr>
<td>
<input type="checkbox" name="ck4">
</td>
<td id="sp4">
Cuatro
</td>
</tr>
<tr>
<td>
<input type="checkbox" name="ck5">
</td>
<td id="sp5">
Cinco
</td>
</tr>
<tr>
<td>
<input type="checkbox" name="ck6">
</td>
<td id="sp6">
Seis
</td>
</tr>
</form>
</body>
</html>
Saludos.