retrieving Group/OU member****p for a user using ADSI/C++

Hello,
 I'm trying to generate a list of groups/OU's to which a user belongs 
through ADSI and am having problems. My AD looks like

DC=FOO,DC=COM
---OU=OrgUnit1
-------CN=GlobalSecurityGroup1
------------------member=CN=User1,OU=OrgUnit1,DC=FOO,DC=COM
------------------member=CN=User2,OU=OrgUnit1,DC=FOO,DC=COM
------------------member=CN=User3,OU=OrgUnit1,DC=FOO,DC=COM
-------CN=User1
-------CN=User2
-------CN=User3
-------CN=BuiltIn
-------CN=Users

So I have a top level OU which contains 3 users, User1,User2 and User3.
The 
OU also contains GlobalSecurityGroup1 which has three members, User1,User2

and User3.

How can I use ADSI to generate a list of OUs/Groups to which User2
belongs? 
I'd like to get a result set of GlobalSecurityGroup1 and OrgUnit1?

I'm able to search DC=FOO,DC=COM and specify the following filter

member:1.2.840.113556.1.4.1941:=CN=User2,OU=OrgUnit1,DC=FOO,DC=COM

which will return the NT Security Group, but not OrgUnit1, do I need two 
different queries?


Thanks!
Michael