Hi @designerfree
This is a bit of a tricky one, but is possible using a filter on the relationship query.
Check out the docs page (http://www.advancedcustomfields.com/resources/tutorials/customize-the-relationship-field-list-query/) and you will find code to alter the results available in the relationship list.
You will need to use this filter to add an exclude argument to the $args. Please research the WP_Query args before doing this.
As for finding the ID’s to exclude, I’m not sure how you will do this.
Good luck
Thanks
E
