I have been assigned the task of redesigning an intranet sight. I have some major obstacles and I am not sure how to proceed.

What I have is a main page designed with menus and CSS formatting.

The major problem is that I am not allowed to change the code on the existing pages. These legacy pages need to be loaded dynamically into my template. The legacy pages are multiple links deep.

I need to know how to insert these pages into my template and keep theme there no matter how deep the user navigates.

I am not permitted to use PHP or frames of any kind including iFrames. CGI & PERL were suggested but I am not very familiar with what they offer. Any suggestions on how to tackle this problem will be appreciated.