Can you catch Entei Suicune Raikou in Pokemon Siver and how?

After you've released them from the tower in ecurteak city they can appear anywhere in the grass. The best way to get one is to go in random bits of grass while using a repel. If your first Pokemon in the party is level 40 only entei raikou and suicune will show up if they are. Your Pokemon that is level 40 should be a gastly/haunter/gengar that knows mean look. This way the Pokemon can't flee. If it manages to flee look in your pokedex. The pokedex will now show the current area the Pokemon is in. If you fly there however it will move. So carry on flying to 1 town and checking the pokedex each time. IF the Pokemon is near go into the grass and get it.