If this is a design time gridview then just add databond column that has binding expression that test the date i.e.
Code:
<%# ((DataItemType)Container.DataItem).DateFieldProperty > SomeDate ? "Expired" : "Not Expired" %>
Where DataItemType is the type of your data item
DateFieldProperty is the property of a DateTime object in your data item
SomeDate is a DateTime object item to test against
You can also do this behavior in code, add the column in the load event, set the value of the column in the data bound event base on what the DataItem