When I am writing Mathematica code in a notebook I often have to go back and forth in order to look up definitions I have given in different places of the notebook. Is it possible to open more than one window to see a single notebook? (I am using Mathematica 7)

Note that I am thinking of a single notebook but several windows. Nothing to do with creating new notebooks from an existing one. Of course, if I change the notebook in one place (through one of the windows) I should see that change instantly through the other windows as well, if they happen to be located on that place.

This exists in editors like Emacs.

Thanks in advance.