How to offset bumpmap like mainTextureOffset

This works great

function Update ()
     renderer.material.mainTextureOffset.x -= transform.root.rigidbody.velocity.z;

But I cannot seem to figure out how to wrangle the bumpmap to follow suit. The access to the bumpMap is considerably more difficult. How can offset the bumpMap based on velocity? Thanks

This is the solution

renderer.material.SetTextureOffset(“_BumpMap”, renderer.material.mainTextureOffset);