Is there a way to grant temporary permission for someone?

 I'm using the Aspnet_regsql.exe for roles in my app.  I want to grant someone temporary permission to access some of the pages in this site for a limited amount of time.  I would like to grant a user permission for a couple days or so, then revoke these permissions.  Or create a user with full permissions that would only last a couple days. 
Is there a way to do this?
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