I’m afraid it’s not currently possible with the Crumble software. There are limit resources on the micro, which makes it a bit tricky. I plan on adding events at some point – i.e. blocks that are similar to the ‘program start’ block, but say ‘when A goes HI’ or similar.
Although, when the Crumble is being controlled from the PC it should be easier. Simon’s ScratchCrumble might already do this?
All the best,