Comparison engine for ASP site

> I run a directory site and am thinking of trying to add the ability to
> compare products listed in each category. e.g. select the products you
> want
> to compare and they appear on the results page, side by side.
>
> The problem I have is that I don't know how to build this comparison
> engine. Does anyone know of any scripts, components, extensions or guides
> I
> can research to help me with this idea?

It'd pretty much just be a DB query returning 2 or more records at a time.

-Darrel