Expanding secondary links menu

I would like the primary links menu to display horizontally across the top of the page, unexpanded. I would also like the secondary links menu to display vertically down the left column, expanding like a normal hierarchical menu as the user navigates deeper and deeper. However, I do not want the primary menu options (the "headers" on the top of the page) to show up in the secondary links menu on the left column. That is, I want the secondary menu on the left column to be entirely context sensitive, depending on which primary links menu item is selected.

Here's an example. Say the primary links menu contains the options "Books," "Movies," and "Music." I would like these options to be presented horizontally across the top of the page. When the user clicks on "Books" in the primary links menu, I would like the left column to display the menu "Genres," "Authors," and "Titles." Then, when the user clicks on "Genres," it expands and shows "Fiction," "Essays," "Poetry," etc. If the user clicks on "Fiction," it expands and shows "Literature," "Mystery," "Romance," etc. If the user then goes back up to the primary links menu and clicks "Movies," then I'd like the left column to display the menu "Directors," "Titles," "By Actor," etc.

My first thought was that I'd just have the primary links menu display on top, and the secondary links menu display on the left. But by default, the secondary links menu doesn't expand. Is there a way to force it to expand as it is navigated? Alternatively, I thought about creating two sets of menus - one for the top primary nav and one for the left secondary nav and somehow customizing them to display as desired - but I didn't have too much luck with that.

Anyone have suggestions? Thanks in advance!