file_column and ftp uploaded files

hi all!
   i have a web application where the user can upload his files
through FTP. It'done and it's ok. Now i want to let the user to select
some ftp uploaded files and make them object in my application (they
are images, so i like for example act_as_attachment plugin
capabilities of making thumbnails automatically). I have strange
errors, because i don't upload files, so my files havent' the
variables (like original_filename) that an upload thourgh a form make
appear.

Now my question: is it possibile to use act_as_attachment or
file_column with "local" files on the server, not using a form to make
the upload?

thanks,
  nelson