:msniwonder:Well a couple months ago I came home from school and thought I heard someone in the house, as a result of this I took rex with me all over the house opened the doors and said check, and he smelled around. I was wondering how I could teach him to check the rooms in the house on command?
You could plan out the route he'd take through the house, and then back-train it. Start with teaching him to go into the last room on command. Then teach him to go into the second-to-last room on command. Then chain those together into one command. Keep adding the earlier rooms, until he's got the whole route down.
Or you could teach him a hide and seek game, where you "hide" a treat in a room where he can see you do it, and release him to "find" the treat. Then put it in a different place, again where he can see you, and repeat. Then, when he can't see you, put it one of those two places and tell him to find it. He should check one place, and then if its not there, check the other.
Build up more and more hiding places, again over a certain route. You should probably be able to get him to search the entire house for the treat on command.
Actually, I'm pretty sure police and military canine units have trained the very behavior you want, but I don't know how. Research time!