ASP Navigation Menu

My project is to make a website that lists all kinds of different items. The Items are sorted into sub categories and the sub categories are sorted into Main Categories. Of course this is all connected to a database

What I need is for the main categories to be presented into a vertical menu then once the mouse is over a Main Category for a menu to appear on the right listing the sub categories and then once the sub category has been clicked a list of items will appear in a form on the center of the page.

I have already been able to connect a wepage to the database and pull off records using SQL statements. I Understand the concept of relationships, primary and foreign keys.