Trouble parsing RECaptcha img URL.

Dim recaptcha_public_key As String = ""
Dim CaptchaAnswerDetails() As String = GetCaptcha(recaptcha_public_key)

Friend Function GetCaptcha(ByVal recaptcha_public_key As String) As String()
        ' Variables
        Dim CaptchaImageURL As String
        Dim URL As String
        Dim Content As String
        ' Load Challenge URL
        URL = "http://api.recaptcha.net/challenge?k=" & recaptcha_public_key
        Try
            Content = Get_URL(URL)
        Catch ex As Exception
            Throw New Exception("Failed To Load Recaptcha Challenge URL: " & ex.Message)
        End Try
        ' Scrape Challenge Key
        Dim ChallengeKey As String = GetBetween(Content, "challenge : '", "'")
        ' Confirm ChallengeKey Exists
        If ChallengeKey = Nothing Then
            Throw New Exception("Failed To Scrape Challenge Key, Unknown Issue")
        End If
        ' Form Captcha Image URL
        CaptchaImageURL = "http://www.google.com/recaptcha/api/image?c=" & ChallengeKey
        ' Form Array
        Dim Keys() As String = {CaptchaImageURL, ChallengeKey}
        ' Return Captcha Image URL
        Return Keys
    End Function