//The error backcolor is displayed if the text contains a single, non-matching parenthesis
FarPoint.Win.Spread.CellStyleNotify cnotify = new FarPoint.Win.Spread.CellStyleNotify();
cnotify.InvalidCellStyle.BackColor = Color.Yellow;
FarPoint.Win.Spread.PairChar pair = new FarPoint.Win.Spread.PairChar();
pair.Left = '(';
pair.Right = ')';
FarPoint.Win.Spread.PairCharValidator pairvalid = new FarPoint.Win.Spread.PairCharValidator();
pairvalid.PairChars.Add(pair);
pairvalid.Actions.Add(cnotify);
fpSpread1.Sheets[0].AddValidators(new FarPoint.Win.Spread.Model.CellRange(1, 1, 1, 1), pairvalid);