Django: How to filter Users that belong to a specific group

I'm looking to narrow a query set for a form field that has a foreignkey to the User's table down to the group that a user belongs to.

The groups have been previously associated by me. The model might have something like the following:

myuser = models.ForeignKey(User)

And my ModelForm is very bare bones:

class MyForm(ModelForm):
    class Meta:
        model = MyModel

So when I instantiate the form I do something like this in my views.py:

form = MyForm()

Now my question is, how can I take the myuser field, and filter it so only users of group 'foo' show up.. something like:

form.fields["myuser"].queryset = ???

The query in SQL looks like this:

mysql> SELECT * from auth_user INNER JOIN auth_user_groups ON auth_user.id = auth_user_groups.user_id INNER JOIN auth_group ON auth_group.id = auth_user_groups.group_id WHERE auth_group.name = 'client';

I'd like to avoid using raw SQL though. Is it possible to do so?