What issue are you facing exactly, I tried running the shader on an object that has default normal mapping applied to them, and then I run the shader, and it still runs on that model. if you can please explain in more detail, maybe I can fix the issue or bug if there is any.
I have a 3d mesh (default box) and have default CC normal mapped textures on it showing the 3D shape that sticks out of the object due to point light lighting - ie it has a 3D look to the textures. This is setup as dynamic lighting of course.
When I add your shader on to it, tried every possible scenario I can think of and when run it removes the 3D look to it totally and only sharpens the normal mapped texture on the surface - ie no real normal mapping at all....are you sure your not confusing sharpening for actually normal mapping ?
Please use a real normal mapped sample when checking that doesnt have smooth surfaces to check...