Internet Cache

Hi All,
I have an app for which the file extension is registered so I can click on the file and run the program. If I am using the file name on a web page with < a ref = url path and name> and click on it and choose to run from the current location,
the file gets downloaded to the cache and the program runs. I would like to get the original URL name inside my app from the cache name.
The API for internet cache seem to only give you local cache name if you give the URL. Is there a way to do the inverse?