Simplified Model of a box on a conveyor belt

[flxbgl]

Hi, I am new to MuJoCo and I want to model the following:

I want to model a conveyor belt transporting a box. I want to simplify my model, by just modeling a static belt of the conveyor (imported static CAD model just for visuals). I want to move the box in one direction on the belt, by applying a velocity on the bottom of the box, without moving the belt. Can anyone help me out with applying the velocity on the bottom of the box?

Thanks!