At my site, I do exactly what I think you want, like this:
* Let it load with the three pages as they normally would.
* The content FRAME tag has an 'id="framec"' attribute.
* The FRAMESET tag has "onload='OtherPage();'" as an attribute.
* If that target exists and is different from the default, I use "window.frames['framec'].location=Target;" to reload that page within the frameset.
I can't create a link to any internal pages in a site that I just took over. All links from elsewhere take me to the default page....
This is why framesets are so hated
If you are concerned about page links from "within" your site then all you need to do is add the "target=" attribute to all your <a> tags to tell the frameset which frame to open the page in. If you leave out "target=" it defaults to top.