def METHOD_NAME(self, request, obj=None, **kwargs):
    form = super().METHOD_NAME(request, obj, **kwargs)
    # this prevents the event field, if any, from showing locked events as a choice
    if not request.user.has_perm('tracker.can_edit_locked_events'):
        queryset = getattr(form.base_fields.get('event', None), 'queryset', None)
        if queryset:
            form.base_fields['event'].queryset = queryset.filter(locked=False)
        for field in self.get_event_child_fields():
            queryset = getattr(form.base_fields.get(field, None), 'queryset', None)
            if queryset:
                form.base_fields[field].queryset = queryset.filter(
                    event__locked=False
                )
    return form