function imgOn(imgName) {
	if (document.images) {
     		onImg = eval(imgName + "on.src");
     		 document[imgName].src= onImg;
    	}
 }

function imgOff(imgName) {
   	if (document.images) {
    		  offImg = eval(imgName + "off.src");
     		  document[imgName].src= offImg;
   	 }
 }