Не могу понять недочет в программе - VB

Public Class Form1
 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
 
        Dim number As Integer = 0   // число, вводимое пользователем
        Dim ch As Integer = 0
        Dim max As Integer = 0
        Dim min As Integer = 9
 
        number = Val(TextBox1.Text)
 
        While (number > 0)
            ch = number Mod 10   
            number = number / 10
 
            If (max < ch) Then
                max = ch
            End If
            If (min > ch) Then
                min = ch
            End If
 
        End While
 
        Label5.Text = Str(max)
        Label6.Text = Str(min)
 
    End Sub
 
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
 
    End Sub
 
End Class