Keep it Collared. Update your oxford by buttoning your blouse all the way up. Then layer your look-at-me bar necklace under the collar so it is just peeking out from underneath the collar.
Make Your Own bar Necklace. If you have a bunch of old brooches lying around, pin them together onto a short chain to create your own bar necklace.
Minimize Distractions. Let your bar necklace shine by avoiding earrings all together (unless they are very subtle posts). Also, gaudy rings and excessive arm flair should be kept to a minimum. When I wear a bold bar necklace,I avoid extra jewelry all together. If anything, I will wear a few simple, thin band rings.