Not sure what your trying to say, but if you mean how do I unselect a selected cell...
for a single cell:
MyGrid[0, 0].Selected = false;
for all selected cells:
if(MyGrid.SelectedCells.Count != 0)
for(int i = 0; i < MyGrid.SelectedCells.Count; i++){
MyGrid.SelectedCells[i].Selected = false;
}
you may need to call invaliate on the DataGridView to reflect the changes.
MyGrid.Invalidate();