Possible to use Wait block to stop loop in My Block?

[nutherbrick]

I've built a My Block that loops runs motors via a Move Tank block. I would like to be able to stop the block based on an external event (such as Ultrasound proximity, or light intensity, etc). At present, I spawn off a parallel loop, look for the condition, then break the loop in the My Block and the parallel loop, which breaks out of the My Block. I would ideally like to use a Wait block attached to my My Block, much like you attach a Wait block to a Move block, but the Wait block never stops the My Block.

Is it possible to use a Wait block to stop the loop in the My Block?