In Silverlight 5 is there a way to call methods on multiple COM interfaces on a COM object ?

I have a COM object that has 2 interfaces ISimpleObject and ISimpleObjectTwo. In Silverlight I am able to get the dynamic handle to the COM object using the progid like this:

 dynamic comObj = AutomationFactory.CreateObject("ATLDllCOMServer.SimpleObject");

However the only methods available on comObj are those in ISimpleObject and none of the methods in ISimpleObjectTwo are available. How can I call methods on ISimpleObjectTwo from Silverlight 5 application ? Both interfaces are dual interfaces.

Appreciate your help!