stackedbar with negatives

From a group with 7 time series variabels (called "bidrag") I get a nice graph with bars for the 6 first variables, and a line for the 7th using:

bidrag.mixed bar(1,2,3,4,5,6) line(7)

However, typically, some of the 6 components in "bar" are negative in a given time period, meaning that

bidrag.mixed stackedbar(1,2,3,4,5,6) line(7)

does not make sense, since the stacking does not sort between positive and negative values. What I am fishing for here is graph where (in each time period) "positives" are stacked in a bar above the zero line, and negatives are stacked in a bar below!

Have I overlooked an option, perhaps?

---