Dynamic drop down and page refresh

[dnml]

I am new to ASP and want to create a page where there are multiple drop down boxes where each subsequent drop down is filtered by the previous drop down. The data that I want to populate the drop downs is to be returned from SQL server. I have managed to create a page where I can do this but it queries the database when the page loads and inserts the values into javascript arrays which are then used for the drop downs. The problem is that 500,000 + records are being returned which makes the page unusably slow. Therefore what I need is guiadnce on how to allow the user to make a selection from a drop down and then the page refreshes (executes a query for the next drop down) and then displays the next drop down on the page. The following article

http://www.4guysfromrolla.com/webtech/061399-1.shtml

suggests this as option 2 a and states that it is truly trivial code. I am so new to ASP that this is even over my head! Does anyone know of a "how to" guide for this or any sample code to do this? I am using Dreamweaver MX.

Thanks in advance, Dan