void __fastcall TForm1::Edit1KeyDown(TObject *Sender, WORD &Key,
      TShiftState Shift)
{
  if(Key==VK_RETURN || Key == VK_DOWN){ // Forward.
    SelectNext(ActiveControl, true, true);
    Key = 0;
  }
  else if(Key == VK_UP){ // BackWard.
    SelectNext(ActiveControl, false, true);
    Key = 0;
  }
}

"혹은"

void __fastcall TForm1::Edit1KeyDown(TObject *Sender, WORD &Key,
      TShiftState Shift)
{
  if(Key==VK_RETURN || Key == VK_DOWN){ // Forward.
    Perform(WM_NEXTDLGCTL,0,0);
    Key = 0;
  }
  else if(Key == VK_UP){ // BackWard.
    Perform(WM_NEXTDLGCTL,1,0);
    Key = 0;
  }
}

"혹은"

void __fastcall TForm1::Edit1KeyDown(TObject *Sender, WORD &Key,
      TShiftState Shift)
{
  if(Key==VK_RETURN || Key == VK_DOWN){ // Forward.
    SendMessage(Handle,WM_NEXTDLGCTL,0,0);
    Key = 0;
  }
  else if(Key == VK_UP){ // BackWard.
    SendMessage(Handle,WM_NEXTDLGCTL,1,0);
    Key = 0;
  }
}