Any broker/agent successfully sue a party who tried to cut you out of commission?

[Leslie Sultan]

I'm wondering if anyone out there has successfully sued a buyer or seller for cutting you out of a commission.  I have a client/Broker who is in this boat (oral agreement ONLY, no written contract, just emails) and I'm looking for successful experiential tips.  Any and all suggestions will be greatly appreciated.  

Thanks.

Leslie Sultan, Esq.