Running total in detail cells of a crosstab

[clearfacts]

Hi,

Is it possible to make Jasper calculate a running total for the detail cells in my Crosstab? I've got one fixed 'Dummy' Row Group and one real Column group (Month) and several financial measures within th e detail cells. For a financial (accounting) report a running total is unmissable.

BTW, I can't do this calculation in SQL as I'm using a custom JRDataSource which doesn 't support this.

I spent half a day searching for this and can 't find it so I suppose this is not possible?

I thought about implementing a JRExtendedIncrementer(Factory) but I guess that won 't make this possible either?

Any suggestions?

Thanks for the help!

Thomas.