Sorry about the mouthful, I'm trying to verbalize the weird and wonderful world of two carriers that are united but not quite. I'll try again:
FIRSTLY, applying UA SWUs to UA flights with CO flight numbers
SECONDLY, that my itinerary will consist, in each direction, of a UA flight with a CO number connecting to a UA flight with a UA number
THIRDLY, that I obviously wish to apply only one SWU in each direction of travel