Create the capture under the interface that you wish (or use any) and add the following advanced filter replacing the 'aaaaaa' with the vendor OUI.
(ether[6:4] & 0xffffff00 == 0xaaaaaa00) or (ether[0:4] & 0xffffff00 == 0xaaaaaa00)
The 1st part is for handling the MAC as a source and the 2nd as destination, if you skip any of the filter parts you'll get only the one direction of the traffic.
