Yii, Update CGridView dataprovider based on AJAX result - php

Question

I'm not sure that I am going about this the right way but here goes.
I have a dropdown list, when I change the values of this list I wish to update the dataprovider of a CGridView via Ajax.
dropDownList
<?php echo $form->dropDownList(
$model,
'assigned_to',
CHtml::listData(Users::model()->findAll(), 'id', 'username'),
array(
'empty' => 'Please Select',
'ajax' => array(
'type'=>'POST',
'url'=>Yii::app()->createUrl('CrmCalendar/Create', array('id'=>$model->model_id,'modelId'=>$model->model, 'updateGrid'=>1)),
'dataType' => 'json',
'success'=>'function(data)
{
alert(data);
$.fn.yiiGridView.update("user-activites-grid", {
data: data
});
}',
),
)
); ?>
CGridView Widget
<?php $this::widget('zii.widgets.grid.CGridView', array(
'id'=>'user-activites-grid',
'ajaxUpdate' => true,
'dataProvider'=>$model->dpUserActivities(),
));
?>
Controller Action
public function actiongetUserActivitesUpdate($id, $modelId)
{
$model=new CrmCalendar;
$model->model = $modelId;
$model->model_id = $id;
if(isset($_GET['updateGrid']))
{
$model->attributes=$_POST['CrmCalendar'];
$newDp = $model->dpUserActivities();
echo serialize($newDp);
}
}
dpUserActivities
public function dpUserActivities($size=20)
{
$date = DateTime::createFromFormat('d/m/Y H:i:s', $this->StartTime);
$date = $date->format('Y-m-d');
$dataProvider=new CActiveDataProvider($this, array(
'criteria'=>array('condition'=>'assigned_to=:assigned_to AND DATE(StartTime) = :date', 'params'=>array(':assigned_to'=>$this->assigned_to, ':date'=>$date),),
'pagination'=>array('pageSize'=>$size,),
'sort'=>array('defaultOrder'=>'Starttime ASC',),
));
return $dataProvider;
}
What I am trying to achieve is that when the drop down for assigned to is changed then the the value is stored back into the $model and the dpUserActivites is re run with the new data and then the CGridView is updated.
Sorry if this makes no sense.
Let me know if you need any more information
Regards.