Cursortasten und TAB auf einer Form abfangen

// *.h

private:
void __fastcall CMDialogKey(TWMKey &AMsg);

protected:
BEGIN_MESSAGE_MAP
VCL_MESSAGE_HANDLER(CM_DIALOGKEY, TWMKey, CMDialogKey)
END_MESSAGE_MAP(TForm)

// *.cpp
void __fastcall TForm1::CMDialogKey(TWMKey &AMsg)
{
    TForm::Dispatch(&AMsg);
    switch(AMsg.CharCode)
    {
        case VK_DOWN : ShowMessage("VK_DOWN");break;
        case VK_UP : ShowMessage("VK_UP");break;
        case VK_TAB : ShowMessage("VK_TAB");break;
    }
}