Question Albedo based on vertex position

Hi.
I have a bunch of boxes that I'm updating every frame to represent some underlying data.
As they are GPU instanced, I'm trying to set up a texture that will let me colour each box based on the number it represents (0 to 1)

I tried to make a shader that uses world position to determine the albedo, but can only get it to work in the fragment mode.


The idea here is that the tallest boxes would be completely green and the shortest ones completely red.

How can I get either the world position of the mesh itself, or of the top vertices, in Shader Graph so I can set a single albedo for each box (per frame)?