[NTG-context] dorecurse within combination

[Henning Hraban Ramm]

Hi, I’d like to place pages from a multipage PDF in a combination:

\startcombination[3*1]
\dorecurse{3}{%
   {\externalfigure[multipage][width=\textwidth/3,page=\recurselevel]}{}
}
\stopcombination

That doesn’t work, because ConTeXt expects a { after \startcombination. 
(“A left brace was mandatory here, so I've put one in.”)
I guess I need some expansion, but \expanded doesn’t help.

How can I do this?

Hraban