ForeignKey dependencies in Django admin

Question

I'm using Django 1.6.4.

I have a Section model that has a ManyToMany relationship with a TimePeriod model. I also have a Question model that has a ForeignKey relationship with the Section model and the TimePeriod model.

What I'd like to do is auto-filter the Section part of the Question form to valid Sections when a given TimePeriod is selected.

For example, if the 2014 TimePeriod contains Section1 and Section2, but the 2013 TimePeriod contains Section2 and Section3, I only want to display Section2 and Section3 in the Section dropdown when 2013 is selected and Section1 and Section2 when 2014 is selected.

First, are there any packages that have been created that do this out of the box? If not, what do I have to do to set this up manually?

Thanks!

Model definitions were requested. They're pretty simple:

section.py

class Section(TimeStampedModel):
    class Meta:
        app_label = 'nps'
        ordering = ('number',)

    name = models.CharField(max_length=255)
    number = models.IntegerField()
    time_period = models.ManyToManyField('TimePeriod',
                                         related_name='sections')

timeperiod.py

class TimePeriod(TimeStampedModel, TimeFramedModel):
    class Meta:
        app_label = 'nps'

    name = models.CharField(max_length=40)

question.py

class Question(TimeStampedModel):
    class Meta:
        app_label = 'nps'
        unique_together = ('time_period', 'number',)

    time_period = models.ForeignKey('TimePeriod',
                                    related_name='questions')
    section = models.ForeignKey('Section', related_name='questions')
    page = models.IntegerField()
    number = models.CharField(max_length=20)
    name = models.TextField()
    slug = models.SlugField(editable=False)

Answer 1

I ended up implementing it as validation on the admin form in the clean() method.