Private Sub WebBrowser1_DocumentCompleted(sender As Object, e As WebBrowserDocumentCompletedEventArgs) Handles WebBrowser1.DocumentCompleted
        Try
            For Each ETIQUETA As HtmlElement In WebBrowser1.Document.All
                If ETIQUETA.TagName = "A" Then
                    If ETIQUETA.OuterHtml.Contains("http://submanga.com/" & TextBox4.Text & "/") Then 
                        Try
                            Dim MIURL As String = ETIQUETA.OuterHtml 
                            MIURL = MIURL.Remove(0, MIURL.IndexOf("href=") + 6)
                            MIURL = MIURL.Substring(0, MIURL.IndexOf(">") - 1)
                            ListBox1.Items.Add(MIURL)
                        Catch ex As Exception
                        End Try
                    End If
                End If
            Next
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try
    End Sub

...
If etiqueta.OuterHtml.ToLower.Contains(String.Format("http://submanga.com/{0}/", "Gakuen Heaven".ToLower.Replace(" "c, "_"c))) Then
...

Private Sub ListBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox1.SelectedIndexChanged
      Navegador.WebBrowser1.Navigate(ListBox1.SelectedItem)
      Navegador.Show()
End Sub