how to check value of relation child table

SqlDataAdapter da1 = new SqlDataAdapter(order_query, conn);        
SqlDataAdapter da2 = new SqlDataAdapter(order_details_query, conn);   
DataSet ds = new DataSet();
da1.Fill(ds,"ORDER");
da2.Fill(ds,"ORDER_DETAILS");
ds.Relations.Add("Details", ds.Tables[0].Columns[0], ds.Tables[1].Columns[0], false);
gridControl1.DataSource = ds.Tables[0];

The order_query has 4 column and the order_details query has 6 column

I want to make read-onlye some column in child table using thi code ,

dataGridView1.Columns[8].ReadOnly=true;

But not working ,  I think I am not check state of the column in child table

Thank's in advance .