randomising displacement

[Balletdude]

I posted this in the file sharing board but need a bit of help to go a bit further with it.
I've been playing with the shader array node, to create a tiled path. I would like to vary the height of some of the blocks, not parts of them for texturing, but the actual height, to give it some randomness. does anyone have any ideas, I thought about using the conditional shader and get position nodes, but nothing seems to work. any thoughts?

[Dune]

Take a look at this thread, there might be some interesting stuff in it for you.

[Balletdude]

I shall have a look. May take a while so I can understand the Maths involved. Have tried recreating one of the node set ups but at the minute they are all the same height still.
But thank you, I think this may be what I'm looking for