I have the following code (runs when a record is added to a form)

if (input.P_liza != null)
{
    input_deal = input.P_liza;
    rec = form_mapping[deal_name == input_deal];
    id = input.N_mero_de_documento_de_Identificaci_n_Alfanum_rico;
    
    contact = -----redacted------.get_crm_contact_by_id(id);
    
    new_row = form_mapping.subform_person();
    new_row.person_name = input.Nombre;
    
    
    rec.subform_person.insert(new_row);
    
}

It works fine... but person_name is a Name field in a subform....

How can I enter the first_name and last_name, it seems it should be trivial (dot notation) but that doesn't work.