Dynamic python Python Dashboard

Question

I am developing a project that requires a form to be created by the size of the amount of item that is created in another form. The initial form is the Formrota:

    class FormRota(forms.ModelForm):
        researcher =forms.ModelChoiceField(queryset=Profile.objects.all(), widget=forms.Select(attrs={'class':'form-control'}) )
   establishment=forms.ModelChoiceField(queryset=Establishment.objects.all(), widget=forms.Select(attrs={'class':'form-control'}))
        product_to_search = forms.ModelMultipleChoiceField(queryset=Product.objects.all(), widget=forms.CheckboxSelectMultiple(attrs={'class':'checkbox-inline'}))
        date = forms.DateField(label='Data do registro', widget=forms.DateInput(attrs={'class': 'form-control', 'placeholder': 'Data de entrada de dados'}))

Let the other form search you:

class FormSeach(forms.ModelForm):
    class Meta:
        model = Seach
        fields = ['rout', 'price_product']

the field price_product needs to be created by the size of the product_to_search who is in Formrota.

Can someone help me, how do I have fields dynamically created in the forms? The version I use is 1.3 of Django!

Grateful!