jFreeChart: Setting different positive and negative standard deviations on a bar chart

I need to create a StatisticalBarChart that not just has one value for standard deviation but a positive and negative standard deviation. So that the deviation is not symmetrical around the mean value. This is how it's supposed to look:

Any ideas? Thanks in advance! alt text http://dl.dropbox.com/u/1144075/Bildschirmfoto%202010-07-25%20u开发者_如何学Cm%2014.05.11.JPG

You'll have to extend BarRenderer to override drawItem() and extend AbstractDataset to provide the extra data, as suggested in the PLSNPAIRS classes, AsymmetricStatisticalBarRenderer and AsymmetricStatisticalCategoryDataset.