Siteminder excel vba authetication

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MS-Excel

SSO

VBA

I need to use jira Rest API to fetch some content in an excel sheet.The problem is that the server is siteminder enabled.I am using this codeproject article as reference (.http://www.codeproject.com/Articles/80314/How-to-Connect-to-a-SiteMinder-Protected-Resource ) but still cannot get to the past the siteminder login page For reference,my code is as follows:

Dim http As New WinHttp.WinHttpRequest
http.Option(WinHttpRequestOption_EnableRedirects) = False
url = "http://example.com"
' Launch the HTTP request
http.Open "GET", url, False
http.Send
target=http.GetResponseHeaders("location")//get the target url for post
Cookie=""
postData="USER="&HttpUtility.UrlEncode(username)&"&PASSWORD="&password
http.Open "POST", target, False
http.setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
http.setRequestHeader "Cookie", Cookie
http.Send postData

The first http request takes me to the userlogin page of siteminder but the user doesn't get autheticated after the post request.I receive the error login page.Any suggestion as to how to get the user autheticated?