Hi:
Since your stored process executes on either the Stored Process server or the Workspace server, these servers do not generally have visibility of or access to files on your local computer's C: drive.
A similar question came up on the forum. Refer to this thread:
http://support.sas.com/forums/thread.jspa?messageID=2821ଅ
The suggested workaround was to FTP the local file to the appropriate server. Tech Support is probably your best bet for help with this question.
Good luck,
cynthia