отключить select в зависимости от значения другого selecta

[vrazbros]

как отключить select в зависимости от значения другого selecta. (Нужно сделать _PAGEFLAKES_imgCounterHolder не активным)

function setCities(chooser) { 
 var pl = document.getElementById("_PAGEFLAKES_imgCounterBlock");
 var mysel = document.getElementById("_PAGEFLAKES_imgCounterHolder");
 var objSel = document._PAGEFLAKES_edit_built_form.WindowSelection;

 if(objSel.value == 'oneFoto') {
 // pl.style.display = "none";
 mysel.disabled = 'true';
 } else {
 pl.style.disabled = 'false';
 } 
}
</script>
<div id="photo_widget">
 <form name='_PAGEFLAKES_edit_built_form'> 
 <label>
 <span class = "bultspan">Open links in:</span>
 <select name="onClickActionHolder" id="_PAGEFLAKES_onClickActionHolder">
 <option value="originalSize" selected="selected">View photo in original size</option>
 <option value="goToSource">Go to source site </option>
 </select>
 </label>


 <label>
 <span class = "bultspan">Anordnung</span>
 <select name="WindowSelection" id="_PAGEFLAKES_WindowSelection" onchange="setCities(this)">
 <option value="oneFoto">Einzelbilder</option>
 <option value="tableFoto" selected="selected">Miniaturansicht</option>
 </select> 
 </label>


 <label id="_PAGEFLAKES_imgCounterBlock" style="display:none">
 <span class = "bultspan">Size of the module</span>
 <select id="_PAGEFLAKES_imgCounterHolder">
 <option value="5">klein</option>
 <option value="10" selected="selected">mittel</option>
 <option value="15">gros</option> 
 </select>
 </label>