[NumLock]

Код:

var
  SaveNotifyEvent: TNotifyEvent;
begin
  if OpenDialog1.Execute then
  begin
    SaveNotifyEvent:=Memo1.OnChange;
    Memo1.Lines.LoadFromFile(OpenDialog1.FileName);
    Label1.Caption:=IntToStr(Length(Memo1.Text));
    Memo1.OnChange:=SaveNotifyEvent;
  end;
end;