Is it possible to add conditions to crafting?

I am trying to figure out if I can set the rations maker to turn bread into rations when bread is above X value. But after fiddling with warehouses pull requests this just seems impossible: since I can't restrict the range at witch the worker pulls resources, they will always be able to steal bread from where the market stall takes its.

Not implemented yet or am I just not smart enough to figure it out?