Encrypted downloadables

Thanks mordauk, for quick reply.In that case can you tell me from which db table the download link is pulled and linked with download button and which page has that downloadabla link so that I can change hyper link to point to different table having encrypted file.

really helpful , also point me where add_query_arg( …. ); apply_filters(); functions are define? also file containing database query to pull that link.

Thanks chriscct..will take a look.!