Stacked column chart

Please help!
I need to chart (stacked column) data that is incremental. The issue is that data can be negative. I need to determine if the data is <, of > 0 because if I used the negative number the chart graphs from the bottom and I lose the incremental data. If the incremental data is positive, then I add the two and goto next. If it contains a negative then I want to see the offset from the previous total less the negative number.... Any ideas?

Classic case of wrong chart for the purpose, maybe?
This sounds more like a case for a Waterfall chart than a stacked column.

http://peltiertech.com/Excel/Charts/Waterfall.html