ช่วยดูโค๊ดตัดสต็อกสินค้าให้หน่อยครับ รันผ่านแต่จำนวนสินค้ายังเท่าเดิมครับ

 Private Sub AddSalePro()
        If tb_emp.Text.Trim = "" Then
            MessageBox.Show("กรุณาระบุรหัสพนักงาน!!!", "ผลการตรวจสอบ", MessageBoxButtons.OK, MessageBoxIcon.Information)
            tb_emp.Focus()
            Exit Sub
        End If

        If tb_mem.Text.Trim = "" Then
            MessageBox.Show("กรุณาระบุรหัสมาชิก!!!", "ผลการตรวจสอบ", MessageBoxButtons.OK, MessageBoxIcon.Information)
            tb_mem.Focus()
            Exit Sub
        End If

        If lv_salepro.Items.Count = 0 Then
            MessageBox.Show("กรุณาระบุสินค้าที่ขาย!!!", "ผลการตรวจสอบ", MessageBoxButtons.OK, MessageBoxIcon.Information)
            Exit Sub
        End If

        tr = conn.BeginTransaction()

        '''''''''''''บันทึกการขายสินค้าของพนักงาน'''''''''''''''''''''
        Dim sqladd As String = ""
        Dim i As Integer
        For i = 0 To lv_salepro.Items.Count - 1

            sb.Remove(0, sb.Length)
            sb.Append("INSERT INTO SaleProduct (Product_ID,Employee_ID,Sdate,Quantity) ")
            sb.Append("VALUES (@proid,@empid,@date,@quantity)")
            sqladd = sb.ToString()

            cmd = New OleDbCommand
            With cmd
                .CommandText = sqladd
                .CommandType = CommandType.Text
                .Connection = conn
                .Transaction = tr
                .Parameters.Clear()

                .Parameters.AddWithValue("proid", lv_salepro.Items(i).SubItems(0).Text)
                .Parameters.AddWithValue("empid", tb_emp.Text.ToString)
                .Parameters.AddWithValue("date", CDate(Date_sale.Value.Date))
                .Parameters.AddWithValue("quantity", lv_salepro.Items(i).SubItems(4).Text)

                .ExecuteNonQuery()
            End With
        Next

        '''''''''''''บันทึกการซื้อสินค้าของสมาชิก'''''''''''''''''''''
        sqladd = ""
        For i = 0 To lv_salepro.Items.Count - 1

            sb.Remove(0, sb.Length)
            sb.Append("INSERT INTO BuyProduct (Member_ID,Product_ID,Quantity,PriceUnit,Bdate) ")
            sb.Append("VALUES (@memid,@proid,@quantity,@punit,@date)")
            sqladd = sb.ToString()

            cmd = New OleDbCommand
            With cmd
                .CommandText = sqladd
                .CommandType = CommandType.Text
                .Connection = conn
                .Transaction = tr
                .Parameters.Clear()

                .Parameters.AddWithValue("memid", tb_mem.Text.ToString)
                .Parameters.AddWithValue("proid", lv_salepro.Items(i).SubItems(0).Text)
                .Parameters.AddWithValue("Ouantity", lv_salepro.Items(i).SubItems(4).Text)
                .Parameters.AddWithValue("punit", tb_price.Text)
                .Parameters.AddWithValue("date", CDate(Date_sale.Value.Date))

                .ExecuteNonQuery()
            End With
        Next

        '''''''''''''การตัดสต็อกสินค้า'''''''''''''''''''''
        Dim QuantityFirst As Integer = 0
        Dim QuantityNow As Integer = 0
        Dim QuantitySale As Integer = 0

        Dim sqlAUp As String = ""
        For i = 0 To lv_salepro.Items.Count - 1

            sb.Remove(0, sb.Length)
            sb.Append("SELECT Quantity From Product WHERE Product_ID=@id")
            sqlAUp = sb.ToString()

            cmd = New OleDbCommand
            With cmd
                .CommandText = sqlAUp
                .CommandType = CommandType.Text
                .Connection = conn
                .Transaction = tr
                .Parameters.Clear()

                .Parameters.AddWithValue("id", lv_salepro.Items(i).SubItems(0).Text)
                .ExecuteNonQuery()
            End With

            Dim dt As DataTable
            dt = New DataTable("Quantity")
            dr = cmd.ExecuteReader
            dt.Load(dr)
            QuantityFirst = CInt(CStr((dt.Rows(0)("Quantity"))))

            QuantitySale = CInt((lv_salepro.Items(i).SubItems(4).Text))
            QuantityNow = QuantityFirst - QuantitySale

            sb.Remove(0, sb.Length)
            sb.Append("UPDATE Product SET Quantity=@quantity WHERE Product_ID=@id")
            sqlAUp = sb.ToString()

            cmd = New OleDbCommand
            With cmd
                .CommandText = sqlAUp
                .CommandType = CommandType.Text
                .Connection = conn
                .Transaction = tr
                .Parameters.Clear()

                .Parameters.AddWithValue("id", lv_salepro.Items(i).SubItems(0).Text)
                .Parameters.AddWithValue("quantity", QuantityNow)
                .ExecuteNonQuery()
            End With

        Next
        tr.Commit()
        MessageBox.Show("บันทึกข้อมูลการขายสินค้าเรียบร้อยแล้ว!!!", "ผลการทำงาน", MessageBoxButtons.OKCancel, MessageBoxIcon.Information)
    End Sub

 Try
                sb.Remove(0, sb.Length)
                sb.Append("UPDATE Product SET Quantity=@quantity WHERE Product_ID=@id")
                sqlUp = sb.ToString()

                cmd = New OleDbCommand
                With cmd
                    .CommandText = sqlUp
                    .CommandType = CommandType.Text
                    .Connection = conn
                    .Transaction = tr
                    .Parameters.Clear()

                    .Parameters.AddWithValue("id", lv_salepro.Items(i).SubItems(0).Text)
                    .Parameters.AddWithValue("quantity", QuantityNow)
                    .ExecuteNonQuery()
                End With
            Catch ex As OleDbException
                MsgBox(ex.Message)
                Exit Sub
            End Try

 Catch ex As Exception
            MessageBox.Show(ex.Message, "ไม่พร้อมใช้งาน", MessageBoxButtons.OK, MessageBoxIcon.Error)
  End Try

sb.Append(“UPDATE Product SET Quantity=”)
           sb.Append(QuantityNow)
           sb.Append(“ WHERE Product_ID=’”)
           sb.Append(lv_salepro.Items(i).SubItems(0).Text)
           sb.Append(“’”)
           sqlAUp = sb.ToString()

           cmd = New OleDbCommand
           With cmd
               .CommandText = sqlAUp
               .CommandType = CommandType.Text
               .Connection = conn
               .Transaction = tr
               .ExecuteNonQuery()
           End With

Try
                sb.Remove(0, sb.Length)
                sb.Append("UPDATE Product SET Quantity=")
                sb.Append("'" & QuantityNow & "'")
                sb.Append(" WHERE Product_ID=")
                sb.Append("'" & lv_salepro.Items(i).SubItems(0).Text & "'")
                sqlAUp = sb.ToString()

                cmd = New OleDbCommand
                With cmd
                    .CommandText = sqlAUp
                    .CommandType = CommandType.Text
                    .Connection = conn
                    .Transaction = tr
                    .ExecuteNonQuery()
                End With