Setting Forms Authenication After using custom login

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ASP.NET

Visual-Studio

I've been searching the web and have not found a way to do this. I need to be able to set the Authenication to true after a user logs in using our university's custom login system.

A little background, I'm using a mixed mode of authenication on a website and the university I work for has a log in system that uses our ads login and a pass phrase and returns a validation ticket. This is not based on logging into ads, this is the university's home grown authenication system.

I need a way that once the user has a valid ticket from the university system to set the authenication mode of the application to true so I can now use the membership and roles from the asp.net controls. Does anyone know of a way to do this? A link to an example or knowledge passed on would be greatly appreciated.

Thanks,
Carolyn