AfterCellUpdate is the right event to use if you're checking on the client.If you're checking server-side, any of the following events will do, depending on whether you want postbacks to occur automatically and when you want the check to be performed: UpdateCell, UpdateCellBatch, UpdateRow, UpdateRowBatchEither way, check the Value of the cell in your checkbox column. Assuming your column's datatype is set to be boolean, the cell's Value will be true if the box is checked, and false otherwise.