function swap(id, newsrc) {
        var theImage = locateImage(id);
        if (theImage) {
                theImage.src = newsrc;
        }
}

function locateImage(name) {
        var theImage = false;
        if (document.images) {
                theImage = document.images[name];
        }
        if (theImage) {
                return theImage;
        }
        return(false);
}