nodeSelectedChanged event notifies about node selection changes.
If you about cell contents modifications - NodeCellChange event is called when cell is changed:
[c#]
private void dataGrid_NodeCellChange(object sender, NodeBase node, int index, object value)
{
Rows rows = sender as Rows;
int row = rows.GetRowFromNode(node);
Column col = rows.Columns.GetColumnFromCellIndex(index);
MessageBox.Show("Cell {0}[Column:{1}], at Row:{2} has been changed with a new value [{3}]", index, col.Caption, row, value.ToString());
}