facebook change label of a request-form-submit

does anyone know how to change the label of a request-form-submit in a facebook application? Right now, my code is:

<fb:serverfbml style="width: 600px;"> 
                    <script type="text/fbml">
                        <fb:fbml> 
                            <fb:request-form
                                action="'.BASE_URL.'index.php?type=Navigation&action=enviar"
                                method="POST"
                                invite="false"
                                type="Tilibra"
                                content="Envia el mensaje SECRETO!"
                                > 
                                <fb:multi-friend-selector  style="width: 170px;"
                                    condensed="true"
                                    email_invite="false"
                                    import_external_friends="false"
                                    actiontext="Envia tu mensaje SECRETO"
                                />
                                <fb:request-form-submit
                                    label="Envia tu mensaje SECRETO"
                                    import_external_friends="false"
                                />
                            </fb:request-form> 
                        </fb:fbml>
               开发者_如何转开发     </script> 
                    </fb:serverfbml>

i want the submit button to have a "Envia tu mensaje SECRETO" label, but instead i get a "Send Tilibra Request"

Thanks a lot :D

figured it out, it only works if you use the "uid" and a %n or %N. I'll leave the question just in case anyone has the same problem