Displaying custom-styled text from the document body in the left margin

[Nebulous]

Here's what I want to accomplish...

Each page within my document displays the text of the previous occurrence of a custom style called ChapterDiv in a rotated text box the left margin of the document.

Here's a more complete explanation...

I have a 100+ page document with chapter divisions. The chapters are not just numbered, they have text-based names.

So, pretend there are 3 chapters (in reality there are many more)
Chapter 1: The Beginning
Chapter 2: The Middle


Chapter 3: The End

I have created a custom style for the chapter divisions. I don't insert page or section breaks - the document is continuous.

Chapter divisions are indicated within this continuous document with text that is formatted by a custom style called ChapterDiv.

I have already successfully created a TOC based upon ChapterDiv.

What I want to do in addition is have Word display the text of most recent occurrence of ChapterDiv in the left margin of each page.

I want that ChapterDiv text to be displayed in a text box in the left margin, with that text box rotated left by 90 degrees so that it is easy to read (I don't need guidance on creating the text box).

Is my description clear enough that you can envision what I want to accomplish?

Short Version: How can I display the text of the most recent occurrence of the custome style "ChapterDiv" in the left margin of each page?