/**
 * Flush the Timeline Express cache when a property is marked as 'sold'.
 *
 * @param  string $new_status New post status.
 * @param  string $old_status Old post status.
 * @param  object $post       Post object.
 *
 * @return null
 */
function timeline_express_clear_transients_on_property_sold( $new_status, $old_status, $post ) {

    if ( 'property' !== $post->post_type || 'sold' !== $new_status ) {

        return;

    }

    // Post ID where the Timeline Express timeline exists
    delete_timeline_express_transients( 1234 );

}
add_action( 'transition_post_status', 'timeline_express_clear_transients_on_property_sold', 10, 3 );