The Call of Duty Profiler is essentially a launcher for Call of Duty 4 Multiplayer which copies your newest profile to whatever version of Call of Duty 4 you are opening. This may or may not keep singleplayer profiles up to date. I can vouch that it works very well with multiplayer profiles, but it may result in out-of-date (or lost progress) on single player profiles. Use at your own risk, and create a backup of your profile (how to do this is explained in the readme file).
More information is included in the zip. Source code (an Xcode project) is also included for those who are interested.