public static object Evaluate(IFormulaExpression Formula)
 {
     return FormulaManager.evaluator.Evaluate(Formula.Elements);
 }
        // TODO comment
        public void SetFormula(IFormulaExpression formula)
        {
            Formula = formula;

            this.isDefault = false;

            if (OnCellSetFormula != null) {
                OnCellSetFormula(this);
            }
        }