在delphi中，如何把MDI工作区的粗边框去掉

在MDI Form中写入如下代码：

interface

TFmMain = class(TForm)

...
    procedure FormCreate(Sender: TObject);

...

private

...
    procedure CreateDefWndProc();
    PROCEDURE ClientWndProc(VAR Message: TMessage);

end;

implementation

...

procedure TFmMain.CreateDefWndProc;
var
  hWnd1 : HWND;
  ccs : TClientCreateStruct;
begin
    ccs.hWindowMenu := 0;
    ccs.idFirstChild := $FF00;
    hWnd1 := CreateWindowEx(WS_EX_CLIENTEDGE,
        'MDICLIENT', '', WS_CHILD or WS_VISIBLE or WS_GROUP or
        WS_TABSTOP or WS_CLIPCHILDREN or WS_HSCROLL or WS_VSCROLL or
        WS_CLIPSIBLINGS or MDIS_ALLCHILDSTYLES, 0, 0, ClientWidth,
        ClientHeight, Handle, 0, HInstance, @ccs);
    FClientInstance := pointer(GetWindowLong(hWnd1,GWL_WNDPROC));
    DestroyWindow(hWnd1);
end;

procedure TFmMain.ClientWndProc(var Message: TMessage);
//VAR
//  MyDC : hDC;
begin
  if (Message.Msg = WM_ERASEBKGND)  then
  begin
    //这儿模拟VCL的源程序用主窗口的背景色填充客户区，
    //你也可以在客户区画一个图形。
    FillRect(HDC(Message.WParam), ClientRect,Brush.Handle);
  //  MyDC := TWMEraseBkGnd(Message).DC;
    //BitBlt(MyDC, (ClientWidth - imBack.Picture.Width)div 2,
     //  (ClientHeight - imBack.Picture.Height) div 2,
     // imBack.Picture.Width, imBack.Picture.Height,
    //  imBack.Picture.Bitmap.Canvas.Handle, 0, 0, SRCCOPY);

    Message.Result := 1;
  end
  else
      Message.Result := CallWindowProc(FClientInstance, ClientHandle,
          Message.Msg, Message.WParam, Message.LParam); 
end;

       
procedure TFmMain.FormCreate(Sender: TObject);
begin
//*******去除MDIchild粗边框**********
  CreateDefWndProc();
  SetWindowLong(ClientHandle, GWL_WNDPROC,
      LongInt(MakeObjectInstance(ClientWndProc)));
  SetWindowLong(ClientHandle,GWL_EXSTYLE,GetWindowLong(
      ClientHandle,GWL_EXSTYLE) and (not WS_EX_CLIENTEDGE));
  SetWindowPos(ClientHandle,0,0,0,0,0,SWP_FRAMECHANGED
      or SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE or SWP_NOZORDER);
//***********************************
end;