function wt(dir) { 
    var text = self.location.href;
    var pos = text.indexOf('wt');
    var num = text.substring(pos+2,pos+5) - 0 + dir;
    num = (num < 10) ? "00" + num : ( (num < 100) ? "0" + num : num);
    window.location.href = text.substring(0,pos+2)  +
                           num + 
                           text.substring(pos+5,text.length);
}