รบกวน ดูโค้ด ในตารางการขาย หน่อยน่ะครับมันยังไม่สมบูรณ์ครับ

Imports System.Data
Imports MySql.Data.MySqlClient

Public Class FrmSale
    Private Sub BtnSeachCus_Click(sender As System.Object, e As System.EventArgs) Handles BtnSeachCus.Click
        Dim sqlQuery As String = "SELECT * FROM Sale WHERE SaleID = '" & TexIDCus.Text & "' "
        MsgBox(sqlQuery)
        Dim sqlAdapter As New MySqlDataAdapter
        Dim sqlCmd As New MySqlCommand
        Dim sqlTable As New DataTable
        'Dim i As Integer

        With sqlCmd
            .CommandText = sqlQuery
            .Connection = con
        End With

        With sqlAdapter
            .SelectCommand = sqlCmd
            .Fill(sqlTable)
        End With
        DataGridView1.DataSource = sqlTable
    End Sub

    Private Sub BtndelCus_Click(sender As System.Object, e As System.EventArgs) Handles BtndelCus.Click
        Dim Query As String
        Query = "INSERT INTO  Sale"
        Dim con As MySqlConnection = New MySqlConnection("Data Source=localhost;Database=tree;User ID=root;Password=123456;")
        Dim sql As MySqlCommand = New MySqlCommand(Query, con)

        Query = "INSERT INTO Sale(SaleAmount,SaleID,SalePrice,ProductName,CustomerID,SaleDate)VALUES("
        Query = Query + TexIDCus.Text + ",'" + TextBox2.Text + "','" + TextBox4.Text + "','" + TextBox3.Text + "','" + TextBox5.Text + "' ,'" + TextBox6.Text + "')"
        con.Open()


        Dim cmd As MySqlCommand = New MySqlCommand(Query, con)
        Dim i As Integer = cmd.ExecuteNonQuery()
        'If (i > 0) Then
        'lblMsg.Text = "Record is Successfully Inserted"
        'Else
        'lblMsg.Text = "Record is not Inserted"
        'End If
        con.Close()
        loadfile()
    End Sub
    Public Sub loadfile()
        Dim sqlQuery As String
        sqlQuery = "Select SaleID as รหัสรายการขาย,SaleAmount as จำนวนการขาย,SalePrice as ราคาในการขายขณะนั้น,ProductName as ชื่อสินค้า,CustomerID as รหัสสินค้า,SaleDate as วันที่ขาย from Sale"

        Dim sqlAdapter As New MySqlDataAdapter
        Dim sqlCmd As New MySqlCommand
        Dim sqlTable As New DataTable
        'Dim i As Integer

        With sqlCmd
            .CommandText = sqlQuery
            .Connection = con
        End With

        With sqlAdapter
            .SelectCommand = sqlCmd
            .Fill(sqlTable)
        End With

        DataGridView1.DataSource = sqlTable

    End Sub

  
    Private Sub DataGridView1_CellClick(sender As System.Object, e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellClick
        Dim i As Integer
        i = DataGridView1.CurrentRow.Index
        TexIDCus.Text = DataGridView1.Item(0, i).Value
        TextBox2.Text = DataGridView1.Item(1, i).Value
        TextBox4.Text = DataGridView1.Item(2, i).Value
        TextBox3.Text = DataGridView1.Item(3, i).Value
        TextBox5.Text = DataGridView1.Item(4, i).Value
        TextBox6.Text = DataGridView1.Item(5, i).Value
    End Sub
    Private Sub FrmSale_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        If con.State = ConnectionState.Closed Then
            con.Open()
        End If
        loadfile()
        con.Close()
    End Sub

    Private Sub BtnAddCus_Click(sender As System.Object, e As System.EventArgs) Handles BtnAddCus.Click
        Dim Query As String
        Query = "INSERT INTO  Sale"
        Dim con As MySqlConnection = New MySqlConnection("Data Source=localhost;Database=tree;User ID=root;Password=123456;")
        Dim sql As MySqlCommand = New MySqlCommand(Query, con)

        Query = "INSERT INTO Sale(SaleAmount,SaleID,SalePrice,ProductName,CustomerID,SaleDate)VALUES("
        Query = Query + TextBox3.Text + "','" + TextBox5.Text + "' ,'" + TextBox6.Text + "')"
        con.Open()


        Dim cmd As MySqlCommand = New MySqlCommand(Query, con)
        Dim i As Integer = cmd.ExecuteNonQuery()
        'If (i > 0) Then
        'lblMsg.Text = "Record is Successfully Inserted"
        'Else
        'lblMsg.Text = "Record is not Inserted"
        'End If
        con.Close()
        loadfile()
    End Sub
End Class

Dim Total As Double = 0
For i As Integer = 0 To DataGridView1.RowCount - 1
        Total += DataGridView1.Rows(i).Cells(2).Value
Next