function add_child_page(page_id) {
    //find and select the page in the parent dropdown
    var selectBox = document.add.parent;
    for (var i = 0; i < selectBox.options.length; i++) {
        if (selectBox.options[i].value == page_id) {
            selectBox.selectedIndex = i;
            break;
        }
    }
    //set focus to add form
    document.add.title.focus();
}