You can also use this filter to filter pages based on their URL. Let's say you have an E-commerce site and all of your E-commerce URL's contain 'store'.
function store_force_ssl( $force_ssl, $post_id = 0, $url = '' ) {
if ( strpos($url, 'store') !== false ) {
$force_ssl = true;
}
return $force_ssl;
}