[]
Gets or sets whether the formula is hidden when the worksheet is protected.
Use this property to control whether cells that use the style hide their formulas after worksheet protection is enabled.
bool FormulaHidden { get; set; }
Property FormulaHidden As Boolean
IStyle style = workbook.Styles.Add("hiddenFormulaStyle");
style.FormulaHidden = true;
worksheet.Range["A1"].Style = style;
bool hidden = style.FormulaHidden;