How can I use a variable from the instance of my data in the upload path for a FileField in my model?

Not even sure if you can do it this way. I'm thinking theres another way like overriding the save or the form_valid function in the view... but I'm trying to use a variable from my instance in my upload path for my file field. If I should do something like override the save method in the view how do I save that in the "upload_to" in my model? 

Here are my model fields

design_ui = models.CharField(max_length=255, default='')
design_document = models.FileField(upload_to='uploads/%Y/%m/%d/(Id like to put the instance design_ui here)', blank=True)

and my view

class GaasWaferDesignCreateView(LoginRequiredMixin, CreateView,):

    fields = ("design_ui", "emitting", "contact_location", "optical_power", "design_date", "designer", "design_document", "designer_ui", "in_trash", "inactive_date", "notes")

    model = GaasWaferDesign

    template_name = 'engineering/gaas_wafer_designs/gaas_wafer_design_form.html'

    def form_valid(self, form):

        object = form.save(commit=False)

        object.created_by = self.request.user

        object.save()

        return super(GaasWaferDesignCreateView, self).form_valid(form)

i.e. if the design_ui of the specific record is GWD0001 and the date is 5/3/18 the upload path would be "2018/05/03/GWD0001/"

Thanks again

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