function SwapImage(sImage) {
    var currSrc = sImage.src;
    var ext = currSrc.substr(currSrc.lastIndexOf("."));
    
    if (currSrc.lastIndexOf('-over') == -1)
        sImage.src = currSrc.substring(0, currSrc.lastIndexOf(ext)) + "-over" + ext;
    else
        sImage.src = currSrc.substring(0, currSrc.lastIndexOf('-over')) + ext;
};