Windows authentication with login form

Question

I want to create a program that will prompt a user for a windows user name and password that authenticates against active directory. Once authenticated I want them to only be able to access particular forms based on their group permissions in active directory. For instance once logged in if they are in the Telnet group they can access the telnet portion of the program if not then they get a generic error telling them to contact their system administrator. They way I see it working is that when they log in it also checks to see what groups they are in and stores it as a variable. Each form that they then access checks that variable and if that group is not listed then the user will not have access to that portion of the program. Thanks for any and all help.