想重载KEYDOWN实现用方向键移动焦点，为什么不好用，求指点

想重载KEYDOWN实现用方向键移动焦点，为什么不好用，求大虾指点
unit   SunEdit;

interface

uses
    SysUtils,   Classes,   Controls,   StdCtrls,   Mask,   Windows,   Graphics,   Messages,   RzEdit;

type
//     TSunEdit   =   class(TRzEdit)
    TSunEdit   =   class(TEdit)
    private
        {   Private   declarations   }
    protected
        {   Protected   declarations   }
        procedure   KeyDown(var   Key:   Word;   Shift:   TShiftState);override;        
    public
        {   Public   declarations   }
        constructor   Create(AOwner:   TComponent);   override;
    published
        {   Published   declarations   }
    end;

procedure   Register;

implementation

procedure   Register;
begin
    RegisterComponents( 'SunComponent ',   [TSunEdit]);
end;

constructor   TSunEdit.Create(AOwner:   TComponent);
begin
    inherited   Create(AOwner);
//     self.FrameVisible:=true;
end;

procedure   TSunEdit.KeyDown(   var   Key:   Word;   Shift:   TShiftState);
begin

    inherited;

  IF   ((KEY=Windows.VK_DOWN)   or   (KEY=Windows.VK_RETURN))   THEN
    begin
      perform(WM_NEXTDLGCTL,0,0);//移动到下一控件
        self.Caption:=inttostr(ord(key));
    end;
    {
  else
  IF   (KEY=Windows.VK_up)   THEN
      perform(WM_NEXTDLGCTL,1,0);   //移动到上一控件
      }

end;


end.

------解决方案--------------------
procedure TForm1.FormCreate(Sender: TObject);
begin
KeyPreview := True;
end;

procedure TForm1.FormKeyDown(Sender: TObject; var Key: Word;
Shift: TShiftState);
begin
case Key of
VK_DOWN: if ActiveControl is TEdit then Perform(WM_NEXTDLGCTL, 0, 0);
VK_UP: if ActiveControl is TEdit then Perform(WM_NEXTDLGCTL, 1, 0);
end;
end;
------解决方案--------------------
IF ((KEY=Windows.VK_DOWN) or (KEY=Windows.VK_RETURN)) THEN
begin
Parent.Perform(WM_NEXTDLGCTL,0,0);//移动到下一控件
// ~~~~~~