//Type a value equal to or less than 10 to see the red line
FarPoint.Win.Spread.LineNotify linen = new FarPoint.Win.Spread.LineNotify();
linen.LineColor = Color.Red;
linen.DoActionReason = FarPoint.Win.Spread.ValidateReasons.EndEdit;
FarPoint.Win.Spread.CompareCellValidator compare = new FarPoint.Win.Spread.CompareCellValidator();
compare.ComparedOperator = FarPoint.Win.Spread.ValidateComparisonOperator.GreaterThan;
compare.Row = 0;
compare.Column = 0;
compare.Actions.Add(linen);
fpSpread1.Sheets[0].AddValidators(new FarPoint.Win.Spread.Model.CellRange(1, 1, 1, 1), compare);
fpSpread1.Sheets[0].Cells[0, 0].Value = 10;