Guessing the year form Directory

A couple of years back I worked out how to guess the year from the directory and I've forgotten how I did it. I'm sure I I worked it out because there was already a subject about it but I can't find anyhting that can help me!
All my albums have the year in front of the title (1970 Paranoid or 1982-08-29 Reading Rock Festival, Thamesside Arena Flac.)
So I used: guess values from %_directory% with the model $left(%year%,4) to extract the year. It's probably really simple but I can't find it and I'm giving up. Can you please help me? I'll kick myself when you tell same as I have been doing since losing my MP3 settings file!!!

Use an action of the type "Format value" for the field YEAR.
Enter as format string: $left(%_directory%,4)

That was quick - thank you. I'll kick myself after taking the dog out for a walk (and no it hadn't crossed my mind to kick him instead!!!)