After a lot of fiddling and thinking (aka tinkering), I finally figured out how to use if statements to control recording and playing of 4 buffers, and on the off chance that this'll be useful to someone else - here it is (and it should be extendeable).
The idea is that there are 4 record/play buffers (not included!) that I want to automatically go into record (only one at once) when audio input goes above a trigger threshold (so that the performer doesn't have to think about any of this). But, as the buffers are [laying back at different speeds, I also don't want to arm a buffer record if that buffer is still playing. I also don't want more than one buffer armed or in record at any one time. (These are short buffers, for granular playback).