[electroly]

I've done this for real, in commercial code that shipped. No trust needed; I have personal experience. For typical minor MessageBox additions, this can be easier than rebuilding the whole dialog yourself. Sometimes, we just wanted to add a "Don't ask again" checkbox which didn't require touching the existing child windows at all. I also used this technique to simply change the labels on the buttons to custom text. I had a MessageBox wrapper that accepted a list of button strings instead of a predefined constant. We've all built various custom message boxes, of course, but not every situation required that level of effort.

These days you can just use a TaskDialog, of course, and it's way more flexible than MessageBox. But it's fun to remember the old techniques.