Its about a guy in prison how get a punisment. He have to move gods know how many rock from one end of the prison yard to the other. And as far as I remember it takes weeks. And when he's done, he have to move them back.
But I can't remember more :(

How old is the movie you're talking about?

Is it maybe Cool Hand Luke (1967) - IMDb (http://www.imdb.com/title/tt0061512/)