Help Adding Trusted Domain user to Trusting Domain Group

[RobinB]

We gave created a web application that uses AD for authorization and
authentication. The application can be used by domain users as well as the
general public. What we currently have is 2 domains - Domain A is the
corporate domain and Domain B is the application domain. Domain B trusts
Domain A.

What we want to do for general public users is to create users in Domain B
(the application) and add them to a group in Domain B. For the corporate
users, we want to add the user account from Domain A (corporate) to the
appropriate Group in Domain B (application). We know that the servers are
setup correctly because we can add users from Domain A (corporate) to a group
in Domain B (application) through the AD management tools.

We are using VB.Net and I know that I need to use DirectoryServices but I
don't really know where to start (As you can probably guess I am not all that
familiar with Active Directory).

What I envision is the following
1. Search for the user object in Domain A
2. Add the found user object from Domain A to the group on Domain B

Any help would be greatly appreciated.

Thanks.