[TYPO3] userFunc doesn't keep values

[Georg Ringer]

Hello,

I just write a userFunc and I have got the problem, that the values doesn't 
get saved:
---- code ----
<?php
class user_class {

    function user_test ($PA, $fobj)    {
     global $BE_USER;

   $ausgabe = '<select name="mode">';
   if ($BE_USER->check("non_exclude_fields",'tx_rgpopup_mode'.":".'simple')) 
$ausgabe .= '<option value="simple">SIMPLE</option>';
   if ($BE_USER->check("non_exclude_fields",'tx_rgpopup_mode'.":".'pro')) 
$ausgabe .= '<option value="simple">PRO</option>';
   if ($BE_USER->check("non_exclude_fields",'tx_rgpopup_mode'.":".'adv')) 
$ausgabe .= '<option value="simple">ADVANCED</option>';
   $ausgabe .= '</select>';

   return $ausgabe;
    }
}
?>
-------- code ------
How can I save my selection?

many thanks
georg