I love Hazel, and this topic has deepened that love

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A question, though: I want to open PAR2 files in the default application when the download of an NZB is finished. The NZB download writes multiple files into a directory, so I want to use the parent directory's modification time to determine when the download is complete.
To do this, I'd like to take the applescript posted by Mr. Noodle, evaluate the mod time of the parent dir, and continue to operate on the file in the dir (the PAR2) if the mod time test passes.
I know I could write an AppleScript to handle everything after detecting the PAR2, but I'd like to keep the logic as encapsulated inside Hazel as possible. Any hints/pointers?