You don;t need to do anything on any event of the first editing control. You might handle the CellValueChanged event and then clear the second combo box cell if its current value is not valid. As for the second combo box, it doesn't exist until the user starts editing a cell in the second column, so you don't need to do anything until then, i.e. when the EditingControlShowing event is raised for that column. At that point AND NOT BEFORE you bind only the appropriate data to only that ComboBox.