How to get unchecked multibox

[Max Mustang]

Hi, i have a list that come from database and i wanna uncheck all the multibox in hand, but whem i´m calling the action that save into the database all the multibox, the fields on the multibox list came as checked, what can i do? sorry my english

 <c:when test="${convenio.globalAsPrimitive}">
    <html:multibox name="EscolherConvenios" property="selectedConvenios">
    <bean:write name="convenio" property="id" />
 </html:multibox>
</c:when>

 public ActionForward processa(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response, Session hibernateSession) {
        EscolherConveniosForm mForm = (EscolherConveniosForm) form;
        Usuario usuario = (Usuario) request.getSession().getAttribute(AbstractSecureAction.HTTPSESSION_USUARIO_LOGADO);
        usuario = (Usuario) hibernateSession.load(Usuario.class, usuario.getId());
        Set<Convenio> convenios = new HashSet();
        String[] x = mForm.getSelectedConvenios();
        System.out.println(x);
        if (x == null) {
        } else {
            for (String s : mForm.getSelectedConvenios()) {
                mForm.reset();
                Convenio c = (Convenio) hibernateSession.load(Convenio.class, Integer.valueOf(s));
                System.out.println(s);
                System.out.println(c.getNome());
                convenios.add(c);
            }
            hibernateSession.save(usuario.getCliente());
        }


        for (Convenio c : mForm.getConvenios()) {
            if (c.getGlobalAsPrimitive() == Boolean.FALSE) {
                convenios.add(c);
            }
        }

        usuario.getCliente().getConvenios().clear();


        usuario.getCliente().setConvenios(convenios);
        hibernateSession.flush();
        return mapping.findForward(SUCESSO);
    }

i really need help´