I often stop robbing by simply closing up the weak hive after dark for 24 hours. The robbers give up trying to get in and look elsewhere and the weak hive get's a respite from the onslaught. 24 hours later (the next night) I open it back up.
Other things that help. I put Vicks vapo-rub near the entrace. Robbers find their way by smell and this is sometimes enough to confuse them.
Robber screens (also useful as skunk screens that confusethe robbers (who are going by smell but don't confuse the residents, who are traveling by memory:http://incolor.inetnebr.com/bush/images/RobberScreenHiveSide.JPGhttp://incolor.inetnebr.com/bush/images/RobberScreenOutside.JPG