Django form class Variables not updating from signals

Question

I'm having a strange issue where it looks like my form is initially built on startup. I've got a variable that changes within it called location, and I can't get it to update properly. I have confirmed that the variable is updated properly via signals, so I just need to get the form to update somehow. Here's the code of the class based form:

class Post(models.Model):
    Priority_Upload = models.FileField(default='priority', upload_to=Profile.location, blank=True, null=True)
    date_posted = models.DateTimeField(default=timezone.now)

    author = models.ForeignKey(User, on_delete=models.CASCADE, related_name='+')
    def __str__(self):
        return self.title
    def get_absolute_url(self):
        return reverse('post-detail', kwargs={'pk': self.pk})

The variable that I have changed is Profile.location. It is initialized in profile as an empty string, "". I change it when the user logs in and on post updates, and in other parts of the code the variable is confirmed to be different. It just looks like when I define my class Post, it does it once and I can't figure out how to update it. Any help would be greatly appreciated. Thank you for your time in advance.