Great! That's got the first part of my answer working!
Now to the second part which involved looking up those illegal characters "/" in the filter search box down the bottom which is all well, except, I only want to search for the illegal characters in the TRACK field not in every search term.
Example: If "/" character appears in the TRACK, ALBUM, ARTIST etc., I only want it to display search results in the TRACK field, how do I do that?
Edit: I have already read Filter expressions with no help so far.
Edit 2: I believe I solved my own question. The answer was %title% HAS "/"