1:n relation between forms and data assignment

1:n relation between forms and data assignment

Hello together,

At the moment, I have three forms:
  1. Form: New Contact
  2. Form: New Car
  3. Form: New Car Rating
In the 'New Contact' form I can create a car by subform 'New Car', so the created Car should be assigned to the Contact.
In the 'New Car Rating' form I can choose a Contact by lookup-field. And now, I need a dropdown-field for choosing only the cars which are assigned to the choosen contact.

I hope everybody understand my problem. In summary, I need a 1:N relation between Contact and Cars and a filtering option on top in other forms.

best regards
Achim