如何关闭和启动explorer.exe？

我的代码如下。问题是，按了button1以后，explorer.exe虽然退出，但马上又启动了。我该如何实现任意开闭explorer.exe呢？
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim myprocesses() As Process
Dim myprocess As Process
myprocesses = Process.GetProcesses
Dim i As Integer
For Each myprocess In myprocesses
If myprocess.ProcessName = "explorer" Then
myprocess.Kill()
End If
Next
Timer1.Enabled = True
End Sub


Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
Shell("explorer.exe")
End Sub