Accessing Values in Multi-Channel Buses

As a supplementary question; I can obviously feed bus values directly into k-rate UGens as args, but is it possible to force local variables inside a SynthDef to be updated whenever the value of a particular bus changes?

I’d like to do some pre-processing of values from a bus, before feeding them into oscillator etc. UGens, and would prefer not to do it “inline”, for readability.