How to prevent duplicate relationship records in HZ_RELATIONSHIPS table

 Hi Guru's

the primary key of hz_relationships table is relationship_id .

this means that we can have multiple/duplicate records of relationships in this table.

how can we ensure that a record of subject_id ( Of type Organization ), Object_id ( of type Person ) , relationship_code ( contact )  be unique in this table ?

we have a situation where a Party-Contact relationship record exists in this table but is end dated. and the system allows the same record to be created again.

this creates some other problems for us.

Is this something that can be prevented by custom pll / forms personalisation ? we are at rel 12.