lpCreateParams Contains additional data which may be used to create the window. If the window is being created as a result of a call to the CreateWindow or CreateWindowEx function, this member contains the value of the lpParam parameter specified in the function call. If the window being created is an MDI window, this member contains a pointer to an MDICREATESTRUCT structure.
Windows NT: If the window is being created from a dialog template, this member is the address of a SHORT value that specifies the size, in bytes, of the window creation data. The value is immediately followed by the creation data. For more information, see the following Remarks section.
