VB.net死循环中使用UI

要实现的功能：在死循环中使用VB的UI界面
窗体构成：1个Form（Form1）:包含两个Button（Button1&&Button2）和一个List（LIstBox1）
运行环境：VS2012
VB代码：
Imports System.Threading
Public Class Form1
Public Declare Function GetTickCount Lib "kernel32" () As Integer
Public Stop_Enable As Boolean
Public n As Integer
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Stop_Enable = False
n = 0
End Sub

        Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
                Do While True
                        If Stop_Enable Then
                                Exit Do
                        Else
                                'hread.Sleep(100)
                                Wait(100)
                                ListBox1.Items.Add(n)
                                ListBox1.TopIndex = ListBox1.Items.Count - 1
                                n = n + 1
                        End If
                Loop
        End Sub

        Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
                If Stop_Enable = True Then
                        Stop_Enable = False
                Else
                        Stop_Enable = True
                End If
        End Sub

        Public Sub Wait(DT As Long)
                Static TT As Long
                TT = GetTickCount()
                Do
                        Application.DoEvents()
                        If GetTickCount - TT < 0 Then TT = GetTickCount
                Loop Until GetTickCount - TT >= DT
        End Sub

        Public Sub Form_Paint()
                Dim a As Control
                For Each a In Me.Controls
                        a.Invalidate()
                Next
        End Sub
End Class

问题：为什么我要点击两下Button2，listbox才停止刷数使据？不是点一下就好了嘛？大神们还有什么好的方法，解决死循环中UI不能使用的方法吗？

求大神指点！！！
C金不多求大神回答啊！

Do While True
Application.DoEvents() '加上这个
...