How to add a Blocked Folder entry for an app in My Protected Files?

I would like to add the Windows directory to the Blocked Files/Folders list of an app, in this case, Winrar.

I added %windir%*; this failed completely, and Winrar extracted into the directory.

I added C:\Windows*; Winrar threw up a dialog stating that it could not write a file, in this case, the .exe in the archive, into the directory. A look at the Windows directory revealed that Winrar was able to create a directory in the Windows directory, and was also able to extract the non .exe files into said directory.

This mechanism by which one would go about restricting folder access to applications is unclear to me; could someone more knowledgeable/experienced help?