using 'steps' in Manipulate

I want to make a 3D shape move through a specified graph; e.g. y = Sin[x], such that it moves up and down.
My working so far has been to use Manipulate, and I think I want to use it with 'steps', as in the documentation, second one down, although I don't know how to use this.
Would this be the way, and if so how do I use it?

Here is what I have so far:

Manipulate[Graphics3D[{Green, Cuboid[{0, 0, t}], Blue, Cuboid[{0, 0, 0}]}], {t, 0, 3}]


I think I want something like:

Manipulate[ Graphics3D[{Green, Cuboid[{0, 0, t}], Blue, Cuboid[{0, 0, 0}]}],
{t, 0, 3, y = Sin[x]}]

-

Manipulate[