[exim] How can i expand a mysql query ?

Hi,
i trying to expand a mysql query and i don?t know exactly how this could be done.
I want to add a "/.spambox" to the result to the spam_delivery mysql lookup.

spam_delivery:
  driver = appendfile
  envelope_to_add
  return_path_add
  mode = 0600
  maildir_format = true
  create_directory = true
  directory = ${lookup mysql{select smtp from users,domains \
        where localpart = '${quote_mysql:$local_part}' \
        and domain = '${quote_mysql:$domain}' \
        and users.domain_id = domains.domain_id}}

The result look like /var/mail/domain/user/Maildir but i need it
like this /var/mail/domain/user/Maildir/.spambox.


Can somebody help me append "/.spambox" to the lookup result without modifying the mysql tables?

Thx in Advance
M.SOYSAL