dovecot - Jul 2010 - address extension going into folder

Is it possible with a simple config change to make address extensions,
e.g. alice+sales at example.com, go into a folder, e.g. .INBOX.sales, and
do so ONLY if that folder already exists (and just go into INBOX if it
does not exist)?

With Postfix, I use
mailbox_command = DOVECOT_LDA -n -e -m "${EXTENSION}"
where DOVECOT_LDA is the path do dovecot's deliver. The -n switch prevents
creation of the IMAP folder.
See http://wiki.dovecot.org/LDA