Post Expiry then to Private Status w/Password

I need a plugin that I can use to mark a post as expired then apply a password that will only be available to supporters. It will make use of existing WP functionality but in a more automated way...

Features needed:
- select time period (days)
- set a post password that admin will set and then create a text file recording URL of post and password that was set.

This would be a quasi "membership" plugin and would prevent me giving away the farm of content I have totally for free.

Open to discussing this...