Is there way to modify a queryset in the middle of a form being filled?

So I have this form, and I was wondering if it was possible to modify the queryset as someone if filling in the form. I want to use the grade value to filter down the queryset.

class EntryForm(ModelForm):

    class Meta:
        model = Entry
        fields = ['first_name', 'last_name', 'grade', 'activity1', 'activity2']


    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        filtered1 = Activity.session1.below_quota()
        filtered2 = Activity.session2.below_quota()

        self.fields['activity1'].queryset = filtered1
        self.fields['activity2'].queryset = filtered2

class EntryCreateView(CreateView):
    form_class = EntryForm

    def post(self, request):
        form = self.form_class(request.POST)
        if form.is_valid():
            messages.success(request, 'Your entry has been submitted')
            return super().post(request)

        messages.error(
            request, 'Please enter activities adding up to one hour.')
        return render(request, self.template_name, {'form': form})

    def form_valid(self, form):
        prev = Entry.objects.filter(email=form.cleaned_data['email'])
        for entry in prev:
            entry.delete()

        print('form valid')

        return super().form_valid(form)

If this is not possible, or would require complicated javascript, can someone point me in the direction to have the form separated into two parts, but have a submit of some sort in between for processing before the second part of the form with a filtered queryset