Plug-in Question

Hi Everyone i have a question regarding freeradius. I am trying to write a plugin and i was wondering what the postauth section is for. I want to be able to alter the authentication decision of freeradius, once it is made but before the ok response is sent. I will use a policy engine to do that and i want to overwrite the final decision if the user is not authorized based on my policy. Is postauth the right place to do this? regards George