ASP.NET Intellisense



General "HOW TO" to question.....

I have an ASP.NET Web App that contains a datalist. What I would like to
accomplish is when the user hovers over a datalist row, or clicks on a
checkbox in that row, display a drop downlist directly below that row similar
to a intellisense dropdownlist. The dropdownlist does not need to be is simply a way to display a list of items for a particular
row (which could number in the 100's). I suppose I could write a HTML title
tag for each row, but the dropdown list would look and feel much better.

Has anyone done this before on the web?? If you could point me in the right
direction (samples, etc) that would be great! I assume the solutions will
rely on heavy javascript, DHTML, css layers, and general HTML - not much