title: How do I filter values in a Django form using ModelForm?
body: <p>I am trying to use the ModelForm to add my data.  It is working well, except that the ForeignKey dropdown list is showing all values and I only want it to display the values that a pertinent for the logged in user.</p>
  
  <p>Here is my model for ExcludedDate, the record I want to add:</p>
  
  <pre><code>class ExcludedDate(models.Model):
      date = models.DateTimeField()
      reason = models.CharField(max_length=50)
      user = models.ForeignKey(User)
      category = models.ForeignKey(Category)
      recurring = models.ForeignKey(RecurringExclusion)
  
      def __unicode__(self):
          return self.reason
  </code></pre>
  
  <p>Here is the model for the category, which is the table containing the relationship that I'd like to limit by user:</p>
  
  <pre><code>class Category(models.Model):
      name = models.CharField(max_length=50)
      user = models.ForeignKey(User, unique=False)
  
      def __unicode__(self):
          return self.name
  </code></pre>
  
  <p>And finally, the form code: </p>
  
  <pre><code>class ExcludedDateForm(ModelForm):
  
      class Meta:
          model = models.ExcludedDate
          exclude = ('user', 'recurring',)
  </code></pre>
  
  <p>How do I get the form to display only the subset of categories where category.user equals the logged in user?</p>