.NET 4Chan Image Scraper

Function GetBetween(ByRef strSource As String, ByRef strStart As String, ByRef strEnd As String, _
    Optional ByRef startPos As Integer = 0) As String
        Dim iPos As Integer, iEnd As Integer, lenStart As Integer = strStart.Length
        Dim strResult As String
        strResult = String.Empty
        iPos = strSource.IndexOf(strStart, startPos)
        iEnd = strSource.IndexOf(strEnd, iPos + lenStart)
        If iPos <> -1 AndAlso iEnd <> -1 Then
            strResult = strSource.Substring(iPos + lenStart, iEnd - (iPos + lenStart))
        End If
        Return strResult
    End Function
    Private Sub ScrapeBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ScrapeBtn.Click
        Dim WebHandle As New System.Net.WebClient
        Dim WebString As String = WebHandle.DownloadString(String.Format("http://boards.4chan.org/b/res/0"))
        Dim WebSplit() As String = WebString.Split("target=")
        Dim ImageCount As Integer = 0
        Dim Filter As String = Nothing
        For Each i As String In WebSplit
            If i.Contains("images.4chan.org") = True Then
                Dim Build_O As String = CStr(GetBetween(i, "//images", """")).Trim
                Dim ID As String = CStr(GetBetween(i, "/src/", "."))
                If Filter = ID = False Then
                    Filter = ID
                    ImageLinks.Items.Add("http://images" & Build_O.Trim)
                    ImageCount += 1
                End If
            End If
        Next
    End Sub