ns4 = (document.layers)? true:false

function preload(imgObj,imgSrc) {
	if (document.images) {
		eval(imgObj+' = new Image()');
		eval(imgObj+'.src = "'+imgSrc+'"');
	}
}

function changeImage(imgName,imgObj,layer) {
	if (document.images) {
		if (document.layers && layer!=null) eval('document.'+layer+'.document.images["'+imgName+'"].src = '+imgObj+'.src');
		else document.images[imgName].src = eval(imgObj+".src");
	}
}