If you don't mind doing this interactively, you could simply get your rep dump and parse it out.
This is obviously keyed to your cookie, so, as i said, it would have to be an interactive process.
You certainly could use the api to do something like this but in order to get the data in a form that will give you the points you want your min/max window would have to be from 1970 to 2050.
Except for the most obscenely reputed users this should not be an issue.
I will bang out another simple usage example for Soapi.JS that will get you started.