Many to May Relationships in Access 2000

I have a database with a many-many relationship. I have built the relavant ‘junction box’ or ‘join table’ to break down the lin to two 1 to many relationships. Fine! My problem is how to populate the tables. The scenario is to add a childs details i.e. name adress etc.. (childid = primary key) For each child there can be many carers so I need to add a carer which is no problem (carerid = primary key), the problem is I need to automatically populate the join table which contains (childid and carerid) but cant seem to get it to work. This is really important and I an desperate to find a solution, can you help!!