You're already setting the R(ead-only) attribute. You could set the H(idden) and S(ystem) attributes in the same way.
desktop.ini files usually just had the H and S (and sometimes A) attributes set, and not R, for what it's worth.
If you want to avoid trashing your clipboard contents each time the button is used, you could use scripting to create the file instead of doing it via the clipboard.