I would like to create a grid of defects that contains fields from the defect model. But I would also like to add some fields into the grid that are not part of the defect model. For example, I want to add a text box or combobox that doesn't exist in the defect model. It would be used for entering values that are then calculated to come up with a defect score that would then be updated into a field that is part of the defect model. How can I do this with the grid component?