Uploading ngen file field with SAEF

<div id="main-text">
                
                <h1>Create a new File for the {embed="_includes/_menu_text_lookup" id="{segment_3}"} chapter</h1>
                {exp:weblog:entry_form weblog="files" return="admin/index" allow_comments="no" allow_trackbacks="no" enctype="multi"}
                    <b>Title<span>*</span>:</b>
                    <input type="text" name="title" id="title" size="50" maxlength="100">
                    <input type="hidden" name="url_title" id='url_title' maxlength="75" size="50" value="{url_title}" />
                    


                    <b>Short Description<span>*</span>:</b>
                    <input type="text" name="field_id_33" id="field_id_33" size="50" maxlength="100">
                    <input type='hidden' name='field_ft_33' value='none' />
                    


                    <b>Full File Description<span>*</span>:</b>
                    <textarea name="field_id_25" id="field_id_25" cols="70" rows="12" maxlength="500" class="tinymce"> </textarea>
                    <input type='hidden' name='field_ft_25' value='none' />
                    


                    <b>File Type<span>*</span>:</b>
                    <select name='field_id_24' class='select' >
                    <option value='Word Document' dir='ltr' >Word Document</option>
                    <option value='Excel Spreadsheet' dir='ltr' >Excel Spreadsheet</option>
                    <option value='PowerPoint Presentation' dir='ltr' >PowerPoint Presentation</option>
                    <option value='PDF' dir='ltr' >PDF</option>
                    <option value='Other' dir='ltr' >Other</option>
                    </select>
                    <div class='hidden'><input type='hidden' name='field_ft_24' value='none' /></div>
                    


                    <input type="hidden" name="field_ft_31" value="none" />
                    <div class='ff-ft' >
                    <div class='ngen-file-field-block'>
                    <input type='file' name='field_id_31' class='ngen-file-input' />
                    <input type='hidden' name='field_id_31[file_name]' />
                    </div>
                    </div>
                    


                    <input type="hidden" name="field_id_11" value="{embed="_includes/_entry_id_lookup" id="{segment_3}"}" />
                    <input type='hidden' name='field_ft_11' value='none' />
                    <input type="submit" name="submit" value="Upload File Now" /><br >

                {/exp:weblog:entry_form}
                
            </div>