character limit in textarea contact form 7

hi i found this code

add_filter( 'wpcf7_validate_textarea', 'character_length_validation_filter', 11, 2 );
add_filter( 'wpcf7_validate_textarea*', 'character_length_validation_filter', 11, 2 );

function character_length_validation_filter( $result, $tag ) {
	$name = $tag['name'];

	if ( ! $result['valid'] )
		return $result;

	if ( 400 < strlen( $_POST[$name] ) ) {
		$result['valid'] = false;
		$result['reason'][$name] = "Too long.";
	}

	return $result;
}

but there is a problem in this code its for all textarea i want this work for specific textarea [textarea* textarea-short] what should i do for that

thankyou

http://wordpress.org/extend/plugins/contact-form-7/