How to let custom meta data (boolean) change if certain tag exists (w Applescript)

Great, thank you!

I was also able now to uncheck entries which don’t have the tag (which I tried in vain for the last hour):

tell application id "DNtp"
	if (selected records) is {} then return
	repeat with theRecord in (selected records)
		set tagMatchedFiles to (selected records whose (tags does not contain "xxx"))
		repeat with theRecord in tagMatchedFiles
			set md to false
			add custom meta data (md as boolean) for "yyy" to theRecord
			exit repeat
		end repeat
	end repeat
end tell