Sorry, we don't have this function here.
I hope you're able to find it somewhere; sounds useful. I suspect it's hard to find because it's one of those things that is much easier to develop in theory than in practice.
"If you drop an egg, you don't say, 'Oh, shoot' and drop the other 11, do you?"
-Source unknown, but obviously brilliant
Reached goal 4/16/2010...but kind of afraid to look these days