title: dynamic FilePathField question
body: <p>I have a model where the location of pdf directory I'm pointing to with my FilePathField is based on the "client" and "job_number" fields.</p>
  
  <pre><code>class CCEntry(models.Model):
      client = models.CharField(default="C_Comm", max_length=64)
      job_number = models.CharField(max_length=30, unique=False, blank=False, null=False)
      filename = models.CharField(max_length=64, unique=False, blank=True, null=True)
      pdf = models.FilePathField(path="site_media/jobs/%s %s", match=".*\.pdf$", recursive=True
  
      @property
      def pdf(self):
              return "site_media/jobs/%s %s" % (self.client, self.job_number)
  
      def __unicode__ (self):
              return u'%s %s' % (self.client, self.filename)
  
      class Admin: 
              pass
  </code></pre>
  
  <p>I've tried to pass the client and job_number data to the pdf field dynamically by using a @property method on the model class, but either my approach or my syntax is fualty because the entire pdf field disappears in the admin. Any pointers on what I'm doing wrong?</p>