If it’s a normal screensaver, the executable has the extension .scr. You’d have to search for a .scr file in the install folder of your screensaver. Adding it to the exceptions might be a bit tricky though since the ‘Add exception’ dialog only displays .exe file. You’d have to browse to the folder that contains the .scr file and they type in the file name manually.
Probably a good idea to always exclude .scr files unless there is a dedicated profile for them. I’ll add that for the next beta release.