overlapping frozen panes?

Hi there, I have seen a worksheet that seemed to have frozen panes that overlap. What I mean by this is that the top row is frozen to start. Then as you scroll down to another major category header, it takes the place of the original frozen header. It stays there until you get to the next major header and so on. I don't have the file anymore but it would be really useful in one I am putting together. anyone know how to do this?