World edit API : Protect region walls

Hi!
I am coding a minigame plugin, and I need some help with the World Edit API. I have read the javacod but I still don't know how to protect the walls of a region.

I have already protected the selected region:

Code:

    public void addRegion(BlockVector b1, BlockVector b2,World w) throws RegionOperationException{
        region = new ProtectedCuboidRegion("bb_" + id,b1,b2);
        manager = getWorldGuard().getRegionManager(w);
        manager.addRegion(region);
        world = w;

The BlockVector b1, BlockVector b2,World w come from the config.yml.

But now I want to protect the walls as a diferent region. How can I do it?

Thanks

 

Ok, Now I think I know what to do, but not how to do it. I have to expand the region one block in all directions and save it as a parent region. I have read the wiki, but I don't understand how can I expand the region.

Thanks

 

Help please !