Ok, I understand.
So now I added this code
    function _cm_getPkeyNames ($pkey_array, $task_id, $pattern_id=null)
    // perform custom processing before the selection string is passed to another form.
    {
        $pkey_array[] = 'fecini';       // append to array
        return $pkey_array;
    } // _cm_getPkeyNames
to class team but the resulting sql in teamp_player_xref still hasn't the field fecini (allthough it's selected when accessing team).