I leveled our bathroom floor before tiling it with ceramic tile and it was quite a lot of work. It wasn't perfect, either. I rented a laser level and grade rod and used a floor leveling compound that you mix with water. I really had to do it inch by inch and it was incredibly time consuming and like I said, just not perfect. It was like paving the bathroom inch by inch. That floor leveler is not cheap either. It's thick and hard to work with. I really think that you would be better off by shimmimg up the un level part and putting plywood over it and then using plastic wood or mortar to level the edges of the plywood. Really, if you're thinking about using that floor leveler stuff, get a couple of opinions first because it didn't work too terribly well.