I need to increment records by 1 and update this in table Ho

Question

This is my code as following
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace FleetManagment
{
    public partial class Driver : Form
    {
        string value1;
        string value2;
        string value3;
        string value4;
       private  int currrecord=0;
       private  int totalrecord=0;
       private bool insertselected;
        DataTable dt = new DataTable();
        DataSet ds = new DataSet();
        SqlDataAdapter da = new SqlDataAdapter();
        SqlConnection con = new SqlConnection();

        public Driver(string str1,string str2,string str3,string str4)
        {
            InitializeComponent();
            value1 = str1;
            value2 = str2;
            value3 = str3;
            value4 = str4;
           
        }
        
        private void fillcontrol()
        {
            textBox1.Text = dt.Rows[currrecord]["DriverID"].ToString();
            textBox2.Text = dt.Rows[currrecord]["DriverName"].ToString();
            textBox3.Text = dt.Rows[currrecord]["Nationality"].ToString();
            textBox4.Text = dt.Rows[currrecord]["Address"].ToString();


        }

        private void Driver_Load(object sender, EventArgs e)
        {
            string constr = "Data Source=" + value1 + ";Initial Catalog=" + value2 + ";User ID=" + value3 + ";Password=" + value4 + "";
            SqlConnection con = new SqlConnection(constr);
            string comdstr = "select * from Driver";
            SqlDataAdapter da = new SqlDataAdapter(comdstr, constr);
            DataSet ds = new DataSet();
            da.Fill(ds, "Driver");
            dt = new DataTable();
            dt = ds.Tables["Driver"];
            currrecord = 0;
            totalrecord = dt.Rows.Count;
            fillcontrol();
        }

        private void NextBtn_Click(object sender, EventArgs e)
        {
           
            if (ds != null)
            {

               currrecord++;
                if (currrecord >= totalrecord)
                {
                currrecord = totalrecord - 1;
                }
               
                    
                fillcontrol();
                label5.Text = currrecord + "of" + totalrecord;

            }
            

           
           }

          private void buttoninsert_Click(object sender, EventArgs e)
          {
                        

          }

                                
      
          }
}
I have driver table this is my fields as following
DriverID  INT
DriverName  nvarchar50
Nationality  nvarchar50
Address     nvarchar50
I have form driver have 4 texbox
textbox1  DriverID
textbox2  DriverName
textbox3  Nationality
textbox4  address
this table have two records
when i press buton next (NextBtn_Click)to go third record it not accept
I need next button increase by 1 if record not exist and update this in table
How i do this
example
if i have two records
1  aln   american  newyork
2  adam   british  british
when i press next button it ok work in records exist but when i press next button to third record it not accept why
what i need is when  press next after 2 it come 3 in text box driver id and update this number in table
How i do that  
please help me