function on_mouse_move(event) {

if (event.clientX > [XSTART] && event.clientX < [XEND]) {
        document.getElementById("cursor_line").setAttribute("display","inherit");
        document.getElementById("cursor_line").setAttribute("transform", "translate(" + event.clientX + ", 0)");
} else {
        document.getElementById("cursor_line").setAttribute("display","none");
}

} function null_handler(event) {}