Rollback using WAL files?

Hi all!

First of all I'm new to this list, please be gentle :-) Next I'd like to
mention that I've already searched the documentation and the archives,
but couldn't find the answer to my question.

I'm running a production/development database using PostgreSQL 8.1 on a
Debian server. Due to some bad code in one of our applications who use
this database, some of the data was modified incorrectly the last few
days. The idea is that I would like to restore the entire database as
much as possible, meaning I would like to undo all transactions that
were performed on it.

Now I've found the WAL files in the pg_xlog directory, and started
browsing around for documentation on what I can do with those. But all I
can find is that you can use them to restore your database after a crash
or a custom backup. But I would like to do it the other way around (not
use them to restore a database, but to roll it back entirely a few
days). I have 4 WAL files, from last Tuesday to today. Can I use these
files to ROLLBACK the current database, so that it's restored to the
situation it was in on Tuesday?

Thanks a lot for any help,

Regards,

Marc