Add combobx in run time and fill another combobox when selected value of first one is changed

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C#3.0

C#

Hi,

I have a datagridview which is bound to the datatable(dtDataCSV). This datatable is filled with values from the excel file which has only 5 col-Date,Bank Desc,Dr,Cr,Bal . dtDataCSV has 7 columns. I have inserted a first combobox at column 5 in datagridview. Now if i select-say third item of the first combobox...then it should add another combobox and fill the corresponding items.

How do i do that?
Below is my code

private void txtSheet_Leave(object sender, EventArgs e)
        {
            try
            {
                if (string.IsNullOrEmpty(txtFileName.Text))
                {
                    MessageBox.Show("Please select file first");
                    return;
                }
                if (string.IsNullOrEmpty(txtSheet.Text))
                {
                    MessageBox.Show("Please write the exact sheet name of excel file");
                    return;
                }

                dtDataCSV = new DataTable();
                DataRow dr;
                dtDataCSV.Columns.Add("TranRefNo", typeof(int));
                dtDataCSV.Columns.Add("Date", typeof(DateTime));
                dtDataCSV.Columns.Add("Bank Desc/Supplier Name", typeof(string));
                dtDataCSV.Columns.Add("Account Code", typeof(string));
                dtDataCSV.Columns.Add("Debit", typeof(double));
                dtDataCSV.Columns.Add("Credit", typeof(double));
                if (comboBox1.Text == "Bank Account")
                {
                    dtDataCSV.Columns.Add("Balance", typeof(string));
                }
                

             

                filHandCSV = new clsFileHandler(txtFileName.Text);

                if (filHandCSV.FileInf.Exists)
                {
                    var connectionString = string.Format("Provider=Microsoft.Jet.OLEDB.4.0; data source={0}; Extended Properties=Excel 8.0;", filHandCSV.FileInf);
                    OleDbDataAdapter adapter = new OleDbDataAdapter("SELECT * FROM [" + txtSheet.Text.Trim().ToString() + "$]", connectionString);
                    DataSet ds = new DataSet();
                    adapter.Fill(ds, "dtref");
                    DataTable dttable = ds.Tables["dtref"];

                    //Load CSV file to dtDataCSV
                    int TranRefNo = 1;
                    if (dttable.Rows.Count > 0)
                    {
                       
                            foreach (DataRow dr1 in dttable.Rows)
                            {
                                // if (dr1[1].ToString() != "" && dr1[2].ToString() != "")
                                if (dr1[1].ToString() != "")
                                {
                                    dr = dtDataCSV.NewRow();
                                    dr["TranRefNo"] = TranRefNo;
                                    dr["Date"] = Convert.ToDateTime(dr1[0].ToString()).ToString("dd MMM yyyy");
                                    dr["Bank Desc/Supplier Name"] = dr1[1];
                                    dr["Debit"] = dr1[2];
                                    dr["Credit"] = dr1[3];
                                    dr["Balance"] = dr1[4];
                                    TranRefNo = TranRefNo + 1;
                                    dtDataCSV.Rows.Add(dr);
                                }
                            }
                        
                        
                    }


                    TranRefNo = 1;
                 

                    dgvLoadExp.DataSource = dtDataCSV;
                    //Formats the date column
                    dgvLoadExp.Columns[1].DefaultCellStyle.Format = "dd-MMM-yyyy";

                    // Add a new Column (Account Head) 
                    DataGridViewComboBoxColumn colAccHead = new DataGridViewComboBoxColumn();
                    Expenses objAccHead = new Expenses();
                    
                    DataTable dt = new DataTable();
                    dt.Columns.Add("catid", typeof(int));
                    dt.Columns.Add("Account Head", typeof(string));
                    dr = dt.NewRow();
                    dr["catid"] = -1;
                    dr["Account Head"] = "";
                    dt.Rows.Add(dr);
                    dt.Merge(objAccHead.getAccountHead());
                    
                    colAccHead.DataSource = dt;
                    colAccHead.HeaderText = "Account Head";
                    colAccHead.DisplayMember = "Account Head";
                    colAccHead.ValueMember = "catid";
                    this.dgvLoadExp.Columns.Insert(4, colAccHead);
                    
                    //Use DataPropertyName to get the selected key column as in :- 
                    this.dgvLoadExp.Columns[4].DataPropertyName = "catid";
                  
                }

            }
            catch (Exception ex)
            {

            }
        }

        private void dgvLoadExp_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            if (dgvLoadExp.CurrentCell.ColumnIndex == 4)
            {
                ComboBox cmb = e.Control as ComboBox;
                cmb.SelectedValueChanged += new EventHandler(cmb_SelectedValueChanged);
            }
        }

        void cmb_SelectedValueChanged(object sender, EventArgs e)
        {
            DataGridViewComboBoxColumn colSubAccHead = new DataGridViewComboBoxColumn();

            Expenses objSubAccHead = new Expenses();
            colSubAccHead.DataSource = objSubAccHead.getSubAccountHead(((ComboBox)sender).SelectedValue.ToString());//Error at this line
            colSubAccHead.HeaderText = "Sub Account Head";
            colSubAccHead.DisplayMember = "SubHead";
            colSubAccHead.ValueMember = "id";
            this.dgvLoadExp.Columns.Insert(5, colSubAccHead);
           
        }

objSubAccHead.getSubAccountHead() returns a datatable whose AccountHead id is selected value,i.e catid

Any help would be really appreciated.
Thanks