Proxy list webbrowser

hey jeg har et problem med et proxy program det skal loade en liste af proxyis over 8000 og så skal den automatisk skifte til næste proxy hvert 30sekund hvordan gør jeg det? lige nu har jeg

Friend Class Form1

    Public Structure Struct_INTERNET_PROXY_INFO
        Public dwAccessType As Integer
        Public proxy As IntPtr
        Public proxyBypass As IntPtr
    End Structure
    <Runtime.InteropServices.DllImport("wininet.dll", SetLastError:=True)> _
    Private Shared Function InternetSetOption(ByVal hInternet As IntPtr, ByVal dwOption As Integer, ByVal lpBuffer As IntPtr, ByVal lpdwBufferLength As Integer) As Boolean
    End Function

    Private Sub RefreshIESettings(ByVal strProxy As String)
        Const INTERNET_OPTION_PROXY As Integer = 38
        Const INTERNET_OPEN_TYPE_PROXY As Integer = 3
        Dim struct_IPI As Struct_INTERNET_PROXY_INFO
        struct_IPI.dwAccessType = INTERNET_OPEN_TYPE_PROXY
        struct_IPI.proxy = System.Runtime.InteropServices.Marshal.StringToHGlobalAnsi(strProxy)
        struct_IPI.proxyBypass = System.Runtime.InteropServices.Marshal.StringToHGlobalAnsi("local")
        Dim intptrStruct As IntPtr = System.Runtime.InteropServices.Marshal.AllocCoTaskMem(System.Runtime.InteropServices.Marshal.SizeOf(struct_IPI))
        System.Runtime.InteropServices.Marshal.StructureToPtr(struct_IPI, intptrStruct, True)
        Dim iReturn As Boolean = InternetSetOption(IntPtr.Zero, INTERNET_OPTION_PROXY, intptrStruct, System.Runtime.InteropServices.Marshal.SizeOf(struct_IPI))
    End Sub

    Private Sub CheckBox1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
        If CheckBox1.Checked = True Then TextBox2.Enabled = True Else TextBox2.Enabled = False
    End Sub

    Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox1.TextChanged
        AcceptButton = Button1
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Select Case CheckBox1.Checked
            Case True
                RefreshIESettings(TextBox2.Text)
        End Select
        WebBrowser1.Navigate(TextBox1.Text)
    End Sub

    Private Sub WebBrowser1_DocumentCompleted(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
        If CheckBox1.Checked = False Then Me.Text = WebBrowser1.DocumentTitle
        If CheckBox1.Checked = True Then Me.Text = "Proxy enabled -{" & TextBox2.Text & "}- " & WebBrowser1.DocumentTitle
        TextBox1.Text = WebBrowser1.Url.AbsoluteUri
    End Sub

    Private Sub WebBrowser1_Navigating(ByVal sender As System.Object, ByVal e As System.Windows.Forms.WebBrowserNavigatingEventArgs) Handles WebBrowser1.Navigating
        Me.Text = "loading..." & TextBox1.Text
    End Sub
End Class

men det kan kun bruge en proxy og skifter ikke automatisk
jeg har ikke noget point som jeg kan give men jeg vil gerne gi nogen når jeg har fået nogen