MOD REQUEST - Trading more than one of the same resource at once

[Bonapartist]

I'm playing a huge map and running Cereal Mills. One of my vassals has 40+ corn and I'd like to trade for it all at once for the Cereal Mills food bonus. The problem is the interface only lets me trade for 1 corn at a time.

Does anyone know a mod that would let me trade for any number of the same resource at once? Would anyone know how to make one?