TO STORE CHECKBOX VALUES IF TRUE(INSIDE A DATAGRIDVIEW) INTO A MYSQL DATABASE

I WANT TO SAVE THE CHECKBOX VALUES IN A PARTICLUAR COLUMN CALLED CHECKBOX IN THE MYSQL DATA BASE WHENEVER THE USER CHECKS THE CHECKBOX AND CLICKS THE SAVE BUTTON.

(I'M USING DATAGRIDVIEW WHICH HAS THESE CHECKBOXES)

ALSO I WANT TO KNOW HOW CAN I RESTRICT THE USER FROM NOT SELECTING MORE THAN 2 CHECKBOXES

THIS IS THE CODE THAT I'VE USED

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using MySql.Data.MySqlClient;


namespace Training_Form
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (sender == button1)
            {
                groupBox2.Enabled = true;
            }

            string constring = "datasource=localhost;port=3306;username=root;password=root";
            MySqlConnection ConDataBase = new MySqlConnection(constring);
            MySqlCommand cmdDataBase = new MySqlCommand("select EMPNO,NAME,DESGN,UNIT from krthik.master where EMPNO = '" + this.textBox1.Text + "'and ELENCASHB = '" + this.textBox2.Text + "' ;", ConDataBase);
            try
            {
                MySqlDataAdapter sda = new MySqlDataAdapter();
                sda.SelectCommand = cmdDataBase;
                DataTable dbDataset = new DataTable();
                sda.Fill(dbDataset);
                BindingSource bSource = new BindingSource();
                bSource.DataSource = dbDataset;
                dataGridView1.DataSource = bSource;
                sda.Update(dbDataset);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // TODO: This line of code loads data into the 'krthikDataSet.training' table. You can move, or remove it, as needed.
            this.trainingTableAdapter.Fill(this.krthikDataSet.training);

        }
    }
}

PLEASE HELP ME!
I'VE SEARCHED ROUND THE NET BUT DIDN'T GET ANY CONVINCING RESULTS!

(I'M NEW TO VISUAL BASIC)