How to insert,update values in datagridview when user clicks the combobox

private void cmbInNa_SelectedIndexChanged(object sender, EventArgs e)
        {
            
            try
            {
            //DataTable dt = pbl.getdatagridview(this.cmbInNa.Text.ToString());
            //if (dt != null && dt.Rows.Count > 0)
                {
                    //cmbInNa.Text = dt.Rows[0]["Function"].ToString();                   
                }
                DataTable dt1 = pbl.getinnm(this.cmbInNa.Text.ToString());
                if (dt1 != null) //&& dt.Rows.Count > 0)
                {
                    dataGridView1.DataSource = dt1;
                    DataGridViewComboBoxColumn cmbkw = dataGridView1.Columns["cmbkw"] as DataGridViewComboBoxColumn;
                    cmbkw.DataSource = dt1;
                    cmbkw.DisplayMember = "KeyWord";
                    DataGridViewComboBoxColumn cmbRetu = dataGridView1.Columns["cmbRetu"] as DataGridViewComboBoxColumn;
                    cmbRetu.DataSource = dt1;
                    cmbRetu.DisplayMember = "col_Return";
                }              
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }     
        }