The AddExcludeHwndEx method adds a window to the skinning exclusion list.  This must be done before the window is shown in order for the exclusion to take effect.

0 = no error
2 = invalid window

Windows are hooked to be skinned after they are shown, so if the window has been shown before AddExcludeHwndEx is called, the window cannot be excluded.
This is the same as AddExcludeHwnd, but it will return a value indicating success or failure.

RemoveExcludeHwnd, SetIncludeorExcludeMode, AddExcludeHwnd