Preline Help

[qma]

Hello, I need a soltion to this problem:

email comes in:
in .qmail-default I have
| preline /usr/bin/check.py
./Maildir/

But what I really want is this:
Only go in the Maildir if check returns a certain result code.
Basiaclly check checks if the email to address is in a certain DB.  If it
is, it puts the message elsewhere and then I do not want it in the
Maildir.
If it isnt in the DB, I want it in the Maildir.

Any ideas on how I can do this?

thanks
Adam