function order_generate_id() {

    var values;

    // first of all we concatenate all relevant inputs
    values  = document.order.ip.value;
    values += document.order.dns.value;
    values += document.order.date.value;
    values += document.order.time.value;
    values += document.order.firstname.value;
    values += document.order.lastname.value;
    values += document.order.street.value;
    values += document.order.plz.value;
    values += document.order.city.value;
    values += document.order.email.value;
    values += document.order.grilltickets.value;
    values += document.order.partytickets.value;
    values += document.order.date.value;
    
    // then we build and MD5 hash of the concatenated string
    // and stores it in the ID field
    document.order.id.value = MD5(values);
}