Are you capturing the data or do you just have the current stage? If you're not capturing the data, you can't report on it. If you're asking how to capture the data I'm thinking a plugin or workflow would be the way to go.
Leon Tribe
Want to hear me talk about all things CRM? Check out my blog
http://leontribe.blogspot.com/
or hear me tweet @leontribe
Want to hear me talk about all things CRM? Check out my blog
http://leontribe.blogspot.com/ or hear me tweet @leontribe