I was hoping for something simple that didn't involve redirecting or rewriting the log file....

I've found a couple of things which might help. I'm going to experiment with them:

- If the irritating app in question can be set to run under a different user name, I think you can set the security policy of that application in such a way so that it doesn't have the "Manage and audit logs" privilege.

- There is a setting under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\EventLog\Application called "SOURCES" which has a list of services which can write to the log. If I'm lucky, simply deleting the offending app from this list will kill its ability to write to the log. Dunno yet, gotta experiment.