Webbrowser1 Navigate Via Textbox Lines Of Text And Urls?

I have the following code that has the webbrowser1.navige via textbox1.text lines of urls:

Public Class Form1
Dim index As Integer = 0

Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
Dim lines() As String = TextBox1.Lines
If index < lines.Count Then
WebBrowser1.Navigate(lines(index))

[Code]...

How do I get the webbrowser to loop back around to line 1 (the url at the top) when it has finished navigating to the last line of text/url?