$ACTIVITIES_LIST = $this->_customdata[1];
        $START_REPETITIONS = 1;
        $MAX_ACTIVITIES = count($ACTIVITIES_LIST);

        $repeatarray = array();

        $activity_group = array();
        $activity_group[] =& $mform->createElement( 'select', 'activity', get_string('form_simple_label_activity',
                                                    'gradereport_scgr'), $ACTIVITIES_LIST);

        $activity_group[] =& $mform->createElement( 'text', 'custom_weighting_activity',
                                                    get_string('form_simple_label_custom_weighting_act_1',
                                                    'gradereport_scgr') );

        $repeatarray[] = $mform->addGroup(  $activity_group, 'activitygroup', get_string('form_simple_label_activity',
                                            'gradereport_scgr'), array(' '));


        $repeateloptions = array();
        $repeateloptions['activitygroup']['helpbutton'] = array('helper_chooseactivity', 'gradereport_scgr');

        $repeateloptions['activitygroup']['custom_weighting_activity']['default'] = '1';
        $mform->setDefault('custom_weighting_activity', '1');

        $repeateloptions['custom_weighting_activity']['disabledif'] = array('custom_weighting', 'eq', 0);
        $mform->disabledIf('custom_weighting', 'custom_weighting_activity', $condition = 'eq', $value=0);

        var_dump($repeateloptions);

        $mform->addHelpButton('activitygroup', 'helper_chooseactivity', 'gradereport_scgr');

        $this->repeat_elements($repeatarray, $START_REPETITIONS,
            $repeateloptions, 'activitygroup_repeats', 'activitygroup_add_fields', 1, null, true);