Itzik:
You can certainly assign a resource for a specific work period on a project
by manually contouring the work distribution in Project. You can also set
the percentage of resource usage on tasks that fall within that time period.
However, there's absolutely no way to keep the schedule from slipping,
taking the resource assignment out of bounds and there's no way to restrict
the resource from applying time against the task outside the boundaries of
the original assignment. This is the price for dynamic schedules and
flexibility. I'm afraid that Managed time periods would be of no help to
you.
The closest you could come to this type of rigidity is to define custom
calendars, but this would only work if Joe worked only on this project and
only for that set amount of time and was unavailable for any other work at
any other time.