Thanks for the pointer. Will try it out later and see what I can find. This is a great forum.
Edit: It is now later and I have tried it out. Once I set that do-not-use-per-pixel-frame checkmark, and then use the UIS2 button dialog I mentioned above, and then remove the "always show the button" and leave the "show the button if there is a help button", then this works perfectly. The button shows up if the programmer of the application has supplied a help button style, and it is not seen otherwise.
Note that I am doing this not because I want to design a skin with help buttons or because I want to write a program that uses these buttons but because one of my most-heavily-used purchased programs (xplorer2) uses these buttons in some dialogs to supply its help information.
So now I am all set, I think, as soon as I make sure that the rest of the skin still works and as soon as I supply a decent graphic decently positioned for the help-button icon.
Again, this is a great forum.