[Страдалецъ]

Вот так попробуй:

Код:

procedure TForm1.StringGrid1DrawCell(Sender: TObject; ACol, ARow: Integer;
  Rect: TRect; State: TGridDrawState);
begin
 if (ACol in [0..StringGrid1.FixedCols-1]) or (ARow in [0..StringGrid1.FixedRows-1])
 then Exit;
 if Trim(StringGrid1.Cells[ACol,ARow]) = ''
 then StringGrid1.Cells[ACol,ARow] := '0'
end;