if (document.images)
   {
     image_off= new Image(100,100);
     image_off.src="_images/nav/subNavArrow.gif";  

     imageOn= new Image(100,100);
     imageOn.src="_images/nav/subNavArrowOver.gif";
     
   }

function change1(picName,imgName)
 {
   if (document.images)
    {
      imgOn=eval(imgName + ".src");
      document[picName].src= imgOn;
    }
 }