I have a grid with Supplier, Month, Cost that shows the past 12 months. In order to sort the months chronologically, I have SortExpression="Year, Mth" for the Month column, which are the numeric values in the query which are not displayed in the grid. This sorts correctly when the Month column header is clicked, but when I drag the Month column to the group bar, it sorts the months alphabetically. How can I get this to sort by Year, Mth when a user groups by the Month column? It seems this should be doable in the RadGrid's GroupsChanging event, but I'm not sure how to make that happen.