[]
Gets a value that indicates whether the formula of the associated IRange object is hidden when the worksheet is protected as displayed in the current user interface.
bool FormulaHidden { get; }
ReadOnly Property FormulaHidden As Boolean
IRange range = worksheet.Range["A1"];
range.Formula = "=SUM(B1:B2)";
range.FormulaHidden = true;
bool formulaHidden = range.DisplayFormat.FormulaHidden;