Try something like:
private void GridCellsChanged(object sender, GridCellsChangedEventArgs e)
{
int row, col;
if(e.Range.GetFirstCell(out row, out col))
{
Console.WriteLine("({0},{1})", row, col);
while(e.Range.GetNextCell(ref row, ref col, false))
{
Console.WriteLine("({0},{1})", row, col);
}
}
}