SH3 Commander 3.2 (the latest one "Thallium Edition")
http://www.subsim.com/radioroom/showthread.php?t=147237 has the Patrol Log Editor built right in. This link
http://www.subsim.com/radioroom/showthread.php?t=133102 will show you how it works, but you no longer have to download it separately.
JScones's first post will show you exactly how to use it. If you have any problems just ask.