por favor, o mais rápido possível

No evento OnKeyPress do form coloque o seguinte codigo:

if key = #13 then
begin
Key:= 0;
Perform(Wm_NextDlgCtl,0,0);
end;

Em properties comolque TRUE em Key Preview

procedure TfrmPri.MudarComEnter(var Msg: TMsg; var Handled: Boolean);
begin
If not ((Screen.ActiveControl is TCustomMemo) or
(Screen.ActiveControl is TCustomGrid) or
(Screen.ActiveForm.ClassName = ´TMessageForm´)) then
begin
If Msg.message = WM_KEYDOWN then
begin
Case Msg.wParam of
VK_RETURN,VK_DOWN : Screen.ActiveForm.Perform(WM_NextDlgCtl,0,0);
VK_UP : Screen.ActiveForm.Perform(WM_NextDlgCtl,1,0);
end;
end;
end;
end;

no evento OnCreate o Form Principal digite a seguinte linha

Application.OnMessage := MudarComEnter;