I have the following ManyManyComplexTableField, which basically form a many to many relationship that allows user to pick number of pages as recommended reading for a given page. Is there a way I can enforce a business rule into this, say user may not select more than 5 pages as recommended reading. Need a way to disable the checkbox I would thought. Any pointer would be deeply appreciated. Cheers.

$tablefield = new ManyManyComplexTableField(
	$this,
	'MyRegionPages',
	'Page',
	array(
		'Title' => 'Page Name',
		'BoldIntroduction' => 'Bold Introduction'
	),
	'getCMSFields_forPopup',
	 "SiteTree.ID != $this->ID AND SiteTree.ParentID=$this->ParentID",
	 'Sort'
);

$tablefield->setPermissions(array(
));


$fields->addFieldToTab( 'Root.Content.FurtherReadings', $tablefield );