una/modules/boonex/tasks/template/popup_form.html

<div class="bx-tasks-form">
    <div class="bx-tasks-form-cnt">
        __form__
        <script language="javascript">
            $(document).ready(function () {
                $("#__form_id__").ajaxForm({ 
                    dataType: "json",
                    beforeSubmit: function (formData, jqForm, options) {
                        bx_loading($("#__form_id__"), true);
                    },
                    success: function (data) {
                        processJsonData(data);
                    }
                });
            });
        </script>
    </div>
</div>