If you can find the Polyhedron with "Beloved of the Lich Queen" there are a series of feats that allow you to make iterative attacks on your attacks of opportunity, it worked just like two-weapon fighting. The first feat allowed you to make on extra iterative attack on your foe (required base attack +6 of course), the second feat two extra iterative attacks on your foe (again, required +11 or better base attack), and the third three extra iterative attacks (required +16 or better base attack). But all attacks had to be directed at a single foe. Though it made Combat Reflexes incredibly scary.