function selectall(nr, value) {
    var elements = Array();
    var subnr = 1;
    var wl;
    while(el = document.getElementById('cb'+nr+''+subnr)) {
        elements.push(el);
        subnr++;
    }

    //for(var i in elements)
    for(var i=0;i<elements.length;i++) elements[i].checked = value;
}