i have a drop down box that lists some departments and based on that department, i want to show the appropriate layer.

Here's what I got so far.

Code:
function ShowDeptExt( dept_id )
 var strDeptID = dept_id.substring(0,1);
 document.write strDeptID;
 
 switch (strDeptID){
 
  case "4":
   // show perfume menu 
   layer_p.style.visibility = "visible";
   layer_s.style.visibility = "hidden";
   break;
  
  case "5" :
   // show shoe menu 
   layer_s.style.visibility = "visible";
   layer_p.style.visibility = "hidden";
   break;
   
  default:
   //show nothing
 }
Nothing fancy, I know, but I'm trying to keep it simple. But what would the code on the Select Box look like? I can't quite figure that part out.

I had something like this, but I know its wrong...
Code:
<select name="dept_id" size="1" class="arial8" OnSelect="ShowDeptExt('502');">
Here are the layers
Code:
<div name="layer_p" id="layer_p" style="visibility: hidden;">
	  Show Perfumes
	 </div>
	 <div name="layer_s" id="layer_s"  style="visibility: hidden;">
	  Show Shoes
	 </div>