GetWindowWord( hWnd, nOffset ) -> <nValue>
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 PARAMETER:

  <hWnd>        Is the handle that identifies the window

  <nOffset>     specifies the zero-based byte offset of the value to be 
                retrieved. Valid values are in the range zero through the 
                number of bytes of the extra window memory, minus 2 (for 
                example, if 10 or more bytes of extra memory were specified,
                a value of 8 would be an index to the fifth integer).
                You can also use these predefines constants:

                 GWW_HINSTANCE   -6 Specifies the instance handle of the
                                    module that owns the window.
                 GWW_HWNDPARENT  -8 Specifies the handle of the parent
                                    window, if any. The SetParent function
                                    changes the parent window of a child
                                    window. An application should not call
                                    the SetWindowWord function to change
                                    the parent of a child window.
                 GWW_ID        -12 Specifies the identifier of the child
                                    window.

 RETURNS:

  The return value specifies information about the given window if the 
  function is successful. 


 DESCRIPTION:

  The GetWindowWord function retrieves a word ( 2 byte )value at the 
  specified offset into the extra window memory of the given window. 
  Extra window memory can be reserved within the RegisterClass function. 


 SOURCE:  

  SOURCE\WINAPI\GETWND.C