Preventing Access to a CHM File

Not sure if this will make sense, but I've had a request to see if there's a way to prevent direct access to a .chm file (i.e. by clicking on it in Windows explorer).

We want to create a separate CHM file for sensitive information. It would not be connected to the main Help system, and would be accessed by a menu link in our software that only high-security users would have.

I asked a similar question a while back, and someone (don't remember who, sorry!) pointed me to a script for adding a password feature. We may still end up using this, but the new request is for something that would simply block any attempt to open it, and ideally give a pop-up message instructing the user that an Admin is needed to view the material (or something similar, I don't think the warning/message has been ironed out yet).

Anyone know of a way to do this?