On a multi-segment flight. Would applying an upgrade instrument to only one segment affect the eligibility to CPU on the remaining segments? I specifically don't want to waste Plus Points on two one hour flights but would still like to be on the CPU list for those flights and request a Plus Point waitlist on a 4 hour flight only.

I searched the CPU and understanding United upgrades threads and couldn't find an answer. It seems to me like the other flights shouldn't be affected but again I couldn't find a definite answer here on FT.