unsticky posts - functions.php

Hello

Using WPMU 2.9.2

We recently noticed one of our more advanced users decided to sticky a post. We'd like to be able to disable this functionality.

I found this post here http://www.theenglishguy.co.uk/2009/04/23/turning-off-sticky-posts/ and tried the suggestion on our dev system but with no luck.

Could anyone point me in the right direction please?

Thanks

Doug