Powerpoint 2007 different header per section

Powerpoint 2007 different header per section

I am trying to create a presentation with different headers depending on
what section of the presentation is currently being shown. At the top of
the slide when viewing a slide that is in section 2 it should show
something like this:
section1 section2 section3 section4
but when viewing a slide in section 1:
section1 section2 section3 section4
Thus creating a section header effect that gives clues to viewers about
current context, similar to many websites.
The "headers and footers" dialogue in the slide master is no use, it only
seems to add headers to the notes page and not to the actual slide.
Meanwhile adding text directly onto the slide master appears universally
on EVERY slide.
Note I am not asking about creating a separate slide to delineate sections.
I'm using Powerpoint 2007 on Windows 7.