[NTG-context] Columns again

Hi everyone, Is there a way to nest two \startcolumns environments, or to define a columnsetspan that "wraps"? What I'd like to do is produce a two column text which is unbalanced on the last page, and then place another two-column text in the last column. I haven't yet found a way to do it in ConTeXt since nesting \startcolumns doesn't seem to work... Cheers Michael