I now understand what you mean, although it did take me several attempts of re-reading your post to get there. but I don't really see the need for such a thing unless your page is going to contain literally hundreds of paragraphs, which it really shouldn't, because it's going to be faster for people to simply scroll up/down than to move the mouse and click on the next/previous button.
Regardless of the practicality, CSS isn't really set up for this kind of thing. It would have to read the position of the page to determine which section a person was currently on and then set the correct page positions for the next/previous buttons. I'm pretty sure this can't be done with just CSS.