IOleServiceProvider.QueryService Returns null

IOleServiceProvider.QueryService Returns null

I am trying to get SHDocVw.InternetExplorer object for the objects in
"Internet Explorer_TridentDlgFrame" below is the code:
private static Guid IID_IWebBrowserApp = new
Guid("0002DF05-0000-0000-C000-000000000046"); private static Guid
IID_IWebBrowser2 = new Guid("D30C1661-CDAF-11D0-8A3E-00C04FC9E26E");
Object webBrowser = null;
serviceprovider.QueryService(ref IID_IWebBrowserApp, ref IID_IWebBrowser2,
out webBrowser);
return (SHDocVw.InternetExplorer)webBrowser;
serviceprovider.QueryService() returns null webBrower.
Please help me...