How to *generate* data for a waterfall chart (not the chart itself)

[trippknightly]

I know how to do a waterfall chart when I already have the data. But I find it a pain to generate the data, say from data organized for a pivot table. I either have to iterate through a pivot table setting a bunch of filters to yes or no and scribing off to the side the numbers or building some kind of cumulative SumIfs statement to generate the totals (actually this latter option isn't horrible). Remember, a waterfall means that as you go "right" in the waterfall you are looking at counts not already included / covered by earlier "drops" in the waterfall to the left.

Would be great if Excel had a waterfall wizard but I don't think it has one. The waterfall is a pre-defined chart type but that assumes you already know your counts that will feed into it.

So, just figured I'd ask... is there some technique/feature I'm missing?