type
  TForm1 = class(TForm)
  private
    { Private declarations }
  protected
    procedure CreateParams(var Params: TCreateParams); override;
  public
    { Public declarations }
  end;

procedure TForm1.CreateParams(var Params: TCreateParams);
const
  WS_EX_NOACTIVATE = $8000000;
begin
  inherited;
  Params.ExStyle := Params.ExStyle + WS_EX_NOACTIVATE;
end;