database - Updating a link table using Access form/SubForm -

i have database has following structure:

pet(pet id, name, type, dob, allergies, etc)

owner(owner id, forename, surname, dob, address, etc)

registered(reg_id, pet_id, owner_id)

the reason structure being remove many many relation whereby pet may have several owners, aim several people responsible animal in question.

my aim have 1 form allows me set 1 owner , pets @ same time (owner pet sub-form), pet should automatically added registration table @ point owner.

other owners added through registration table itself.

any suggestions on how in access? i'm trying avoid stating pets can have single owner.

thanks