Maybe I'm not getting your idea that well... but what I do is use PhP to do something like that.
For example, I have a website that has around 100 pages, and each page has the same navigation menu at the right. If I want to edit a link on that menu, I'd have to change all the 100 pages... but what I do is make just 1 page for the menu, and on all the 100 pages I just put a where I want my menu to appear and voila! you just have to change that one file
I hope that's what you mean...