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Gets or sets the value or expression associated with the second part of a conditional format or data validation.
The returned object represents the second comparison value for rules that use two operands, such as data validation rules that use Between or NotBetween. It can be a constant value, a string value, a cell reference, or a formula.
object Formula2 { get; set; }
Property Formula2 As Object
IValidation validation = worksheet.Range["A1"].Validation;
validation.Add(ValidationType.Whole, ValidationAlertStyle.Stop, ValidationOperator.Between, 1, 10);
object formula2 = validation.Formula2;