Switching between buffers in split windows

[Felix E. Klee]

Hi,

I already asked this on comp.emacs a couple of days ago but got only one 
reply via email from someone who misunderstood my post. Now, the message:

Often, I split an EMACS window horizontally into two windows to edit two 
different portions of the same buffer *A*. Sometimes, I need to temporarily 
switch to another buffer *B* via "C-x b" in one of the windows. This works 
fine and quick. However, hitting "C-x b" again doesn't return me to where I 
came from, but instead displays another buffer *C* because *A* is already 
displayed. Of course, this is how it's supposed to work, but I want to 
change that behavior:

How do I make "C-x b" redisplay the portion of *A* that I was editing 
previously?

Felix