Using Google Currency Converter - how?

I'm using a currency converter and having some problems passing the variable. Can you take a look to the url please?
protected void btnGoogleApi_Click(object sender, EventArgs e) { decimal amount = 0; string fromCurrency; string toCurrency; amount = decimal.Parse(txtAmount.Text.Trim(), System.Globalization.NumberStyles.Any, CultureInfo.InvariantCulture); fromCurrency = ddlFrom.SelectedItem.Value; toCurrency = ddlTo.SelectedItem.Value; if (amount != 0) { WebClient web = new WebClient(); string url = string.Format("https://www.google.com/finance/converter?{0}/{1}/{2}", amount, fromCurrency.ToUpper(), toCurrency.ToUpper()); string response = web.DownloadString(url); Regex regex = new Regex("rhs: \\\"(\\d*.\\d*)"); decimal rate = System.Convert.ToDecimal(regex.Match(response).Groups[1].Value); l ...