Cycle through AJAX search results using downkey

I'm having issues figuring a way to cycle through results returned as part of an ajax search.
When someone presses a key, the .asp page runs SQL against the database and returns the results inside a <div>.

At this point, I'd like to be able to use the down key to go through the list, but I'm not sure how.

Here's my code:
      

if (document.getElementById('searchText').value == ""){
		 document.getElementById("search_suggest").innerHTML="";
	 }
	 if (str.length==0)
	   { 
	 	document.getElementById("search_suggest").innerHTML="";
	   return;
	   }
	   
	 if (window.XMLHttpRequest)
	   {// code for IE7+, Firefox, Chrome, Opera, Safari
	   xmlhttp=new XMLHttpRequest();
	   }
	 else
	   {// code for IE6, IE5
	   xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
	   }
	 xmlhttp.onreadystatechange=function()
	   {
	   if (xmlhttp.readyState==4 && xmlhttp.status==200)
		 {
		 document.getElementById('search_suggest').style.display="block";
		 var ss = document.getElementById('search_suggest')		
		 ss.innerHTML = '';		
		 ss.innerHTML = xmlhttp.responseText;		
		 		
		 
		 //document.getElementById("search_suggest").innerHTML=xmlhttp.responseText;
		 }
	   }
	 xmlhttp.open("GET","showsearchresults_home.asp?"+str,true);
	 xmlhttp.send();
	
}

//Mouse over function
function suggestOver(div_value)
 {	
 	div_value.className = 'suggest_link_over';
 }
 
//Mouse out 
function suggestOut(div_value) 
 {	
	div_value.className = 'suggest_link';

} 
  
//Click function
function setSearch(value) 
{	
document.getElementById('searchText').value = value;	
document.getElementById('search_suggest').innerHTML = '';
document.getElementById('search_suggest').style.display="none";
}

Select allOpen in new window

"search_suggest" is the ID of the DIV where the results are displayed, right under the text box where the search text is entered.

I hope this makes sense what I'm asking.
Any help would be appreciated!