Directory Services, LDAP or similar

I and a group of developers of my company are defining the user authentication method of an application we are building.

In other projects, we managed the user authentication by creating tables that define all users and its allowed capacities, then the application queryies that data to verify if a user has access to some feature or not. But yesterday one of my coworkers said that we can leave all that stuff in the hands of MS Directory Services or LDAP, i know we can control the user permissions to the whole application using that tecnology, but can we interact with a service like that to give access to some parts of the program, like a particular dialog or screen?

Thanks in advance,
Leonardo M. Ramé
http://leonardorame.blogspot.com
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