HANDLE hThread;
unsigned ThreadId;
volatile bool exitflag;
HANDLE formHandle;
int counter =  0 ;
//---------------------------------------------------------------------------
unsigned __stdcall ThreadFunc(void* ArgList)
{
    exitflag = false;
    while( !exitflag )
    {
        Sleep( 500 );
        PostMessage(formHandle,WM_USER+ 1 , 0 , 0 );
    }
    return  0 ;
}
//---------------------------------------------------------------------------
void __fastcall TFThreadTest::BtnStartClick(TObject *Sender)
{
    hThread = (HANDLE)_beginthreadex(NULL,  0 , ThreadFunc, NULL,  0 , &ThreadId);
}
//---------------------------------------------------------------------------
void __fastcall TFThreadTest::FormCreate(TObject *Sender)
{
    formHandle = Handle;
}
//---------------------------------------------------------------------------
//ловим WM_USER+1, присланный из потока
void __fastcall TFThreadTest::Msg(TMessage &Message)
{
    Label->Caption = IntToStr(++counter);
}
//---------------------------------------------------------------------------
void __fastcall TFThreadTest::BtnStopClick(TObject *Sender)
{
    exitflag = true;    
}
//---------------------------------------------------------------------------