for each dummy
-----ball ID==Dummy ID--->ball:rotate around dummy.
If that doesn't work in C2, try this (I mostly use classic, so I'm not sure if c2 has small differences with regards to picking)
for each dummy
---for each ball
-----ball ID==Dummy ID--->ball:rotate around dummy.
alternatively you can store the dummy co-ords in 2 PVs in the balls, and get rid of the dummy objects altogether. This is less flexible because you can't manipulate the dummies around like normal objects (you need to reference the balls by ID grouping, then change all of their PVs at once), but you save on object count, which can help in a restricted environment (like phones).