This method does not return a value.

The window style must be changed after calling this function on a window. The simplest way to do this is to hide and show the window using the Windows ShowWindow API.
The AddExcludeHwnd method adds a window to the skin exclusion list.  This must be done before the window is shown in order for the exclusion to take effect.

AddExcludeHwnd, SetIncludeorExcludeMode