Hi Karunas,
I think you can post your question in forums of Install Shield, I believe that there are more specialized engineers who can provide professional solution about how to add Custom Action into MSI by using Install Shield.
However, based on my experience, if you are using VS.NET, you can find the registry key of IE7’s trusted websites and add your website into it by defining a custom action in .NET’s Setup Project.
Hope it helps.
Thanks.
Best wishes,
Jun Wang