Reversing transactions in the SQL transaction log

Okay, another esoteric question for ya:

My client recently (well, the middle of January, anyway) attempted to restore their year-end backup to do some reporting, only to find that the backup file was corrupted and unrestorable. They do have earlier monthly backups, but they do not keep transaction log backups past those monthly backups (i.e. transaction log backups for November are discarded once the monthly full backup has been completed).

My question is this: is there any way to restore the month-end backup from January, then read the transaction log backups for the month of January to undo January's transactions?

This is a highly business-critical issue; they are going to be in a lot of hot water with the SEC if they can't produce the financials stored in the DB.

This is a SQL 2000 SP4 database.

Thanks!

Possible with thirdparty tools if you have completed logs.