Looping through parent GridView and hide some columns of nested GridView using C# in ASP.Net

Dear All

I have a GridView and Nested GridView with Records. I want to loop through the GridView, and Hide Some Columns of the Nested GridView based on Who is Actually loged in (this is check by User Email).

Below is the script:

NESTED GRIDVIEW:

<asp:GridView ID="GridViewGroup" runat="server" DataKeyNames ="GroupID" OnRowCreated="GridViewGroup_RowCreated"

CODE BEHIND: Method of Nested GridView:

        protected void GridViewGroup_RowCreated(object sender, GridViewRowEventArgs e)
        {
                GridView gvOrders = sender as GridView;

                if (e.Row.RowType == DataControlRowType.DataRow)
                {
                    if (User.IsInRole("Konferanse_Read") || User.IsInRole("Konferanse_Update") || User.IsInRole("Konferanse_Delete"))
                    {
                        string constr = ConfigurationManager.ConnectionStrings["DatabaseVestConnectionString1"].ConnectionString;
                        SqlConnection con = new SqlConnection(constr);

                        SqlCommand cmd;

                        con.Open();

                        string courseId = GridView1.DataKeys[0].Values["CourseID"].ToString();


                        string checkChildOwner = "SELECT AdminOfficerOfCaseEmail FROM konferanse_Register WHERE CourseID =@CourseID";

                        cmd = new SqlCommand(checkChildOwner, con);
                        cmd.Parameters.AddWithValue("@CourseID", courseId);

                        string valueChildOwner = cmd.ExecuteScalar() as string;

                        MembershipUser memberEmail  = Membership.GetUser();
                        string AdminEmail           = memberEmail.Email.Trim();

                        if (valueChildOwner != null && !valueChildOwner.Equals(AdminEmail))
                        {
                            gvOrders.Columns[1].Visible = false;
                            gvOrders.Columns[3].Visible = false;
                            gvOrders.Columns[4].Visible = false;

                        }

                        con.Close();
                    }
                }
        	}

The above solution only works for one records of Main GridView.

How to resolve the issue?

Many thanks in advance