[Dovecot] Dovecot quota dict

[Juan Bernhard]

Hi, Im using dovecot with maildir++ quota and I have this problem, maybe 
some of you already solve this and can helpme.
I want to use some flat file to tell exim and dovecot the quota limit 
for each user, i tried to work with exim and maildirsize file, but exim 
just ignores the limits there.
I need a way (a really simple one, i dont want to create a database or 
an ldap server just for this) to tell exim and dovecot to lookup some 
file to get the quota limits. I know how to doit with exim, now i need 
to know how to tell dovecot to read the quota limits from this file. I 
know that dovecot can read the quota limit from the userdb, but im using 
pam and i dont want to change the entire auth schema.
Can I configure dovecot to get the quota limit from a file using pam as 
userdb?

Thanks, Juan.

pd: here is my doveconf -n

# 2.0.13: /usr/local/etc/dovecot/dovecot.conf
# OS: Linux 2.6.18-238.9.1.el5 x86_64 CentOS release 5.6 (Final) ext3
auth_cache_size = 10 M
auth_debug = yes
auth_verbose = yes
base_dir = /var/run/dovecot/
default_client_limit = 5000
default_process_limit = 1000
disable_plaintext_auth = no
listen = *
login_greeting = Server ready.
mail_debug = yes
mail_location = maildir:/var/mail/%u:INDEX=~/
mail_plugins = quota
maildir_very_dirty_syncs = yes
passdb {
   args = failure_show_msg=yes %s
   driver = pam
}
plugin {
   mail_log_events = delete undelete expunge copy mailbox_delete 
mailbox_rename
   mail_log_fields = uid box msgid size subject
   quota = maildir:Cuota de correo
   quota_rule = *:storage=1G
   quota_rule2 = Trash:storage=+100M
}
protocols = imap pop3
service auth {
   client_limit = 12000
}
service imap {
   process_limit = 5000
}
service pop3 {
   process_limit = 5000
}
ssl = no
ssl_cert = </etc/ssl/certs/dovecot.pem
ssl_key = </etc/ssl/private/dovecot.pem
userdb {
   driver = passwd
}
protocol imap {
   imap_client_workarounds = tb-extra-mailbox-sep tb-lsub-flags
   mail_plugins = quota imap_quota
}
protocol pop3 {
   pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
   pop3_lock_session = yes
   pop3_uidl_format = %08Xv%08Xu
}