How To Update Multiple Checkboxes In Another Model

Hi everybody and thanks for reading .

I have a Create form where i create meeting's. Each meeting has some participants that are saved on bridge table.

This is the code i use on the Meetings controler to insert a new meeting and the participants to the meeting ;

public function actionCreate()
	{
		$model=new Meeting;
               
		if(isset($_POST['Meeting']))
		{
			$model->attributes=$_POST['Meeting'];
                        
                      
			if($model->save())
                            //upload the partecipants
                                $partecipants = $_POST['Meeting']['partecipants'];    
                          if(!empty($partecipants))  
                            {
                            
                                foreach($partecipants as $partecipant){
                                        $bridge=new BridgeWg();
                                        $bridge->id_wg=$model->id_wg;
                                        $bridge->id_user_registry=$partecipant;
                                        $bridge->save(false);
                                }
                            }
                                                     
				$this->redirect(array('view','id'=>$model->id_wg));
		}

		$this->render('create',array(
			'model'=>$model,
		));
	}

in the view i have the following code

 <?php echo $form->checkBoxListInlineRow($model, 'partecipants', CHtml::listData(UserRegistry::model()->findAll(), 'id_user_registry', 'firstname')); ?>

"partecipants" is a filed not present in the db so i defined it as public $participants in the model Meetings

Anybody has an idea how i can load the participants on the update page and have all the boxes checked of the participants i inserted during the creation of the Meeting.
Let me know if anybody has an idea or a link i could reffer to .
Thanks in advance