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GridWorksheet.Validations.Add() method. Using this method, you must specify the cell range. However, if you want to create a data validation in a single GridCell, you can do it directly using the GridCell.CreateValidation() method. Similarly, you can remove Data Validation from a GridCell using the GridCell.RemoveValidation() method.
The following sample code creates a Data Validation in cell B3. If you enter any value that is not between 20 and 40, cell B3 will display a validation error in the form of Red XXXX, as shown in this screenshot.

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