It took me about three minutes to create the expression I posted, and I have very little experience with the syntax and I am not a mathematician (indeed the question in your word document meant nothing to me).
The way I did it was to select some similar items from the editor and then tweak them until it worked as per your example. If you are a mathematician then it is potentially useful to understand that syntax.
Having said all that, the filter suggested by German sounds very interesting and may save great deal of time. If it does work for you please post in this discussion to confirm.