Group box on a tab control

Let's get this out of the way... I'm doing this in C++ using the Windows API, no MFC or anything like that. The controls are using Comctl32.dll 6.0, giving them the XP visual style.

Now, I've got a tab control on a dialog, which has a group box on it. The groupbox's text label has a background, right? Well, this background, instead of being transparent, is being drawn with a solid color background, which matches the color of the dialog background. I've tried just about everything to attempt to get it to just draw transparent. If I make the group box a child of the tab window, I can get it to be transparent that way, but... I was wondering if there was some way to get it to work without doing so.

Also, I noticed that the built-in dialogs for Date/Time, Network Connection Properties, and things like that all have tabs with group boxes on them that have transparent text label backgrounds. Using Spy++, you can see that all of the controls on each tab are displayed on an invisible dialog. I'm pretty sure these are actually "Property Sheets", but that's not what I want to use. If they can get it to work in the system dialogs, there must be SOME way of doing it.

Any help would be greatly appreciated.