Ccheckbox Column Values Through Javascript/jquery

<?php
$form=$this->beginWidget('CActiveForm', array(
'id'=>'ConsultationNew',
'enableAjaxValidation'=>false,
'enableClientValidation'=>true,

));
?>

echo CHtml::submitButton('PrintSites', array('name' => 'PrintSites','onclick'=>'return Sendchk()'));

$this->widget('zii.widgets.grid.CGridView', array(
'id'=>'consultation-new',
'dataProvider'=>$model->search(),
'summaryText' => 'Displaying {start} - {end} of {count} result(s).',

'filter'=>$model,

'columns'=>

array(
array(
'class'=>'CCheckBoxColumn',
'id'=>'chk',
'selectableRows'=>'50',
//'htmlOptions'=>array('width'=>'40px'),

),
<?php $this->endWidget(); ?>
<script>
function Sendchk()
{
$('#ConsultationNew').attr('action',"index.php?r=ConsultationNew/printsites");
$('#ConsultationNew').submit();
}
</script>


I want to check whether any checkboxes are selected or not when some one clicks the print button without selecting any check boxes and I want to give an alert message when it is clicked. Is there any way to do it with ccheckboxcolumn?