procedure TForm1.FormCreate(Sender: TObject);
var
  DialogUnitsX: LongInt;
  PixelsX: LongInt;
  i: integer;
  TabArray: array[0..4] of integer;
begin
  Memo1.WantTabs := true;
  DialogUnitsX := LoWord(GetDialogBaseUnits);
  PixelsX := 20;
  for i := 1 to 5 do
  begin
    TabArray[i - 1] := ((PixelsX * i) * 4) div DialogUnitsX;
  end;
  SendMessage(Memo1.Handle, EM_SETTABSTOPS, 5, LongInt(@TabArray));
  Memo1.Refresh;
end;