How can I find which user is running local installed drop box application in windows platform.

Thank you for reply.
I think I was not able to explain the scenario properly.
Scenario:
My server authenticate drop box account, when our user register with us. We store its auth key in database.
My client only uses local drop box folder on windows machine to copy the files. So DBX automatically upload or download the files with DBX server.But problem is , how can I come to know that my local drop box account user is same as server drop box user. I mean can I use any API from drop box and cross check. The %APPDATA%\Dropbox\info.json file do contain the "host" field, Can I use this.