Option Explicit On 
Option Strict On
Public Class Form1
    Inherits System.Windows.Forms.Form

#Region " Windows Form Designer generated code "

    Public Sub New()
        MyBase.New()

        'This call is required by the Windows Form Designer.
        InitializeComponent()

        'Add any initialization after the InitializeComponent() call

    End Sub

    'Form overrides dispose to clean up the component list.
    Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
        If disposing Then
            If Not (components Is Nothing) Then
                components.Dispose()
            End If
        End If
        MyBase.Dispose(disposing)
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
        '
        'Form1
        '
        Me.AutoScaleBaseSize = New System.Drawing.Size(5, 13)
        Me.ClientSize = New System.Drawing.Size(200, 109)
        Me.Name = "Form1"
        Me.Opacity = 0.1
        Me.Text = "Form1"

    End Sub

#End Region

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim input As String
        Dim Another As Integer
        Dim sales, Commission As Double

        Do While (Another <> 7) ' If user click [No] --> exit loop
Begin:
            input = InputBox("Enter the sales amount ")
            If input = "" Then GoTo WantEnd 'If Cancel --> Ask to Another 
            If input.Chars(0) = " " OrElse input.ToLower <> input.ToUpper OrElse input.Length > 20 Then 'Avoid letters & Empty space Another and more than 20 digits 
                MessageBox.Show("Invalid Value        ", "  Error...", MessageBoxButtons.OK, MessageBoxIcon.Error)
                GoTo Begin
            End If

            ' *** Calculations ***
            sales = Val(input)
            Select Case sales 'Select the proper case and Calculate the Commission 
                Case 1 To 100000
                    Commission = sales * 0.02
                Case 100001 To 200000
                    Commission = 2000 + (sales - 100000) * 0.04
                Case 200001 To 300000
                    Commission = 6000 + (sales - 200000) * 0.06
                Case 300001 To 400000
                    Commission = 12000 + (sales - 300000) * 0.08
                Case Is >= 400001
                    Commission = 200000 + (sales - 400000) * 0.1
            End Select
            'Show Message with Commission result
            MessageBox.Show("For a Sales amount of --------> " & Format(sales, "currency") & ControlChars.Cr & ControlChars.Cr & ControlChars.Cr & "The Commission amount is ---> " & Format(Commission, "currency") & "                  " & ControlChars.Cr, "Marshall Solution 2.0", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
WantEnd:
            Another = CInt(MessageBox.Show(" Calculate another one ?         ", "Marshall Solution 2.0", MessageBoxButtons.YesNo, MessageBoxIcon.Question))
            'MessageBox.Show(" " & Another, "", MessageBoxButtons.OK, MessageBoxIcon.None)
        Loop

        Me.Close()
    End Sub
End Class