var Images = new Array(3);

    Images[0] = "img/DUNAS-cero_ord.gif";
	Images[1] = "img/DUNAS-uso_esp.gif";
	Images[2] = "img/DUNAS-uso_gen.gif";
	Images[3] = "img/DUNAS-uso_res.gif";
	Images[4] = "img/DUNAS-zon_exc.gif";
	
  for (i=0; i < aryImages.length; i++) {
    var preload = new Image();
    preload.src = Images[i];
  }

  function carga(imgIndex, imgTarget) {
   document[imgTarget].src = Images[imgIndex];
   }