Need workaround for belongs_to :finder_sql

Hi

I am building an interface around my postfix config files. I have a bit of a mix of primary keys with the "Mailboxes" table having a rails-esqe Id field for each user. However, my "Aliases" table has just From/To email addresses.

I would like to be able to add a couple of "belongs_to" attributes to the Aliases model object which will give me a user object for both the From or To email addresses. Any suggestions on how to do this (or even if it's worth bothering really... Just add finer methods...?)

Cheers

Ed W