function tree(val,button)
{
   if( button.src.indexOf("+.gif") > 0 )
      changeImage( val,button,'-' )
   else
      changeImage( val,button,'+' )
}
function changeImage(val,button,mode)
{
   if( mode=='-')
   {
      button.src = "/images/-.gif";
      if(val!=null) on(val);
   }
   else
   {
      button.src = "/images/+.gif";
      if(val!=null) off(val);
   }
}

function on(val) 
{
   // get specific div item, identified by node index
   var itm = document.getElementById(val);
   var txt = document.getElementById(val+"text");

   // turn on menu tip display
   txt.style.display="block";
}

function off(val) 
{
   // get specific div item, identified by node index
   var itm = document.getElementById(val);
   var txt = document.getElementById(val+"text");

   // turn off menu tip display
   txt.style.display="none";
}