procedure Test;
begin
  MyThreadCriticalSection.Enter;
  Try
    inc( Counter );
    while not (qbytes= 1000) do
    begin
      Application.ProcessMessages;
      inc(qbytes);
      Sleep(1);
    end;
  Finally
    qbytes:=0;
    MyThreadCriticalSection.Leave;
  End;

  Unit1.Form1.Label1.Caption:=IntToStr(Counter);
end;

procedure TForm1.Timer1Timer(Sender: TObject);
var
  merkeEnabled:Boolean;
begin
  merkeEnabled:=Timer1.Enabled;
  Timer1.Enabled:=false;
  Test;
  Timer1.Enabled:=merkeEnabled;
end;


procedure TForm1.Button1Click(Sender: TObject);
begin
  Test;
end;