[NTG-context] columnsetspan - alternative needed

Hi, as far as I've seen columnsets work in a magazine like style: \startcolumnset[twocolumns] aaa ... \startcolumnsetspan[heading] bbb \stopcolumnsetspan ccc ... \stopcolumnset gives results like this: aaa ccc aaa ccc bbbb ccc ccc ccc ccc But how can I structure columnsets so my result will look like this?: aaa aaa aaa aaa bbbb ccc ccc ccc ccc Thank you, Steffen