ดูโค้ดหักภาษีให้หน่อยคะ ถ้าเราจะเขียนการหักภาษีไปด้วยนะคะ ไม่รุว่าจะเขียนตรงส่วนไหนดีนะคะ

Option Explicit On
Option Strict On
Imports System.Drawing.Drawing2D

Public Class fromCalculator

    Public Sub New(ByVal CurrentString As String)
        InitializeComponent()
        lblPaid.Text = CurrentString
    End Sub

    Private Sub fromCalculator_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Label1.BackColor = Color.FromArgb(0, 0, 0, 0)
        Label2.BackColor = Color.FromArgb(0, 0, 0, 0)
        Label3.BackColor = Color.FromArgb(0, 0, 0, 0)
        Label6.BackColor = Color.FromArgb(0, 0, 0, 0)
        Label4.BackColor = Color.FromArgb(0, 0, 0, 0)
        Label7.BackColor = Color.FromArgb(0, 0, 0, 0)
        Label5.BackColor = Color.FromArgb(0, 0, 0, 0)
        Label8.BackColor = Color.FromArgb(0, 0, 0, 0)

        txtCash.ContextMenu = New ContextMenu()
       ' txtVATRate.ContextMenu = New ContextMenu()


        txtCash.Text = "0"
        lblExchange.Text = "0"
       ' txtVATRate.Text = "7"

    End Sub

    Private Sub txtCash_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtCash.TextChanged
        'เหตุการณ์ใสจำนวนเงินที่รับมา
        If lblPaid.Text.Trim() = "" Then lblPaid.Text = "0" 'จำนวนเงินที่ต้องชำระ
        If txtCash.Text.Trim() = "" Then txtCash.Text = "0" 'รับเงินที่ชำระมา
        If lblVate.Text.Trim() = "" Then lblVate.Text = "0" 'ภาษี
        
        If CDbl(txtCash.Text) = 0 Then
            lblExchange.Text = "0" 'เงินทอน
            Exit Sub
        End If

        lblExchange.Text = (CDbl(txtCash.Text) - CDbl(lblPaid.Text)).ToString("#,##0.00") 'แสดงจำนวนเงินทอน
       ' lblVate.Text = CSng(txtCash * (CSng(txtVATRate.Text) / 100)).ToString("#,##0.00") 'แสดงภาษี

    End Sub

    Private Sub txtCash_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles txtCash.KeyPress
        e.Handled = CurrencyTextBox.CurrencyOnly(txtCash, e.KeyChar)
    End Sub

    'Private Sub cmdClose_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdClose.Click
    '    Me.Close()
    'End Sub

    Protected Overrides Sub OnPaint(ByVal e As System.Windows.Forms.PaintEventArgs)
        Dim lgb As New LinearGradientBrush(ClientRectangle, Color.Yellow, Color.LawnGreen, LinearGradientMode.Vertical)
        e.Graphics.FillRectangle(lgb, ClientRectangle)
        lgb.Dispose()
    End Sub
End Class