How can I change just one language string in WordPress?

 
add_filter( 'gettext', 'wpsc_my_string_changes', 10, 3);
function wpsc_my_string_changes($translation, $text, $domain ){
	if( $domain == 'geodirectory' && $text == 'Post received, your listing may need to be reviewed before going live, you can preview it %shere%s.' ){
		$translation = 'Thanks for adding a listing this will be approved within 24 hours.';
	}
	return $translation;
}