Where do you make pokeblocks?

Find a contest hall if your playing ruby and sapphire the contest halls are in: Verdanturf Town, Fallarbor Town, Slateport City, Lilycove city. If your playing Emerald there is only one contest hall which is in Lilycove City go inside the contest hall and find the square machine near it will be an old man and some other people stand in the spot where no people are and check the machine choose yes to start berry blending now choose any berry from your bag and once the other players put there berries in the game will start notice the red arrow near your name and the red arrow that is moving press the A button when its near your red arrow keep doing this until the blender stops you will receive a pokeblock. *Note* None of this can be done without the Pokeblock Case.