How do you reference another character's caster level in a buff?

This is in Pathfinder if that matters. So I'm trying to add a buff for Fly which grants +1 for every 2 caster levels on character B, but this is cast by character A. To do this I need to know character A's caster level (because of multiclassing and negative levels this won't be the same as character B's level). So far I've tried the following; none of which work: +(floor(@{characterB|caster1_level}/2) to fly Creating an ability named characterBCasterLevel which is "@{characterB|caster1_level}". Testing this with Roll Ability works on character A, adding it to the buff does not Adding an Attribute on character A called Character_B_Caster_Level which does @{characterB|caster1_level}, referencing this in places like damage as a test does work, but it doesn't work in the buff. Thoughts? Help?

So I spotted this after rereading the docs: " Buffs using attributes (or aliases) not listed will be ignored." In my case character A doesn't need a @{caster2_dcbonus_level_9} (which is listed and not ignored (I double checked)) so I set that to @{characterB|caster1_level}, but that's not working either. But calling @{character A|caster2_dcbonus_level_9} in chat is working