[NTG-context] (repost) How to put float caption header in margin?

Hi all, I fear to re-post this request, but I've read (well, tried to read) page-flt.tex and I still am not certain what to do (or what to override) to do this. The <command> key of \setupcaptions is not useful, as it seems to pass the entire caption (including the header part) as a single argument: How can I put the header part only of a float caption (i.e., the "Figure 6" bit) in the left margin (so as to match \setupheads [alternative=inmargin]), but leaving the caption text part in the normal place? Robin