Add user to an Active Directory security group using an UPDATE trigger

One way you could do this is by running WMI scripts through XPCmdShell in your trigger.

Read more on the WMI script here:

http://gallery.technet.microsoft.com/ScriptCenter/en-us/b9c5914e-86cc-4b2b-8b7d-6a82ab2b465d

There are multiple issues with this, though:

1. It will make your Updates slower because now you have to shell out, then open a trigger
2. In most well set up SQL Server environments XPCmdShell is disabled because opens up security holes - Good luck on getting your DBA to open that one up for you.