[NTG-context] TOC columns

Hi there, I've got a table of contents for a document that's split into two large sections. I'm trying to display a centered heading for each section, and subsections listed in two columns underneath each section heading. Hopefully this illustrates something of what I'm trying to achieve: \midaligned{Section1} \startcolumns[n=2] Subsection1 ... \stopcolumns \midaligned{Section2} \startcolumns[n=2] Subsection1 ... \stopcolumns Does anyone know how to automate this for a table of contents? Thanks for any help :) Paul