Prevent Last row in DatagridView from Sorting

Hi,

i have a datagridview which is populated with a DataTable & i am inserting a row  to show sum of 1 column values inside it (in DataTable) and then providing it as Datasource to the datagridview.

the last row is nothing but "Total : %Number of records%          %Sum Value%".

when the gridview sorts the above row is also sorted which i guess is obvious.

how can i prevent the above from sorting. 

is there sumthing wrong in inserting a summary row in datatable itself, if so whts the other option to have similar functionality.

Thanks

ST