[NTG-context] Quick Metapost question

[Olivier]

Hi all,

I'm looking for an equivalent of \externalfigure[width=1mm]
but for \reuseMPgraphic. Something like 
\reuseMPgraphic[width=1mm]{my-mp-drawing}

There is always the way of tracking the generated file and including it
with exernalfigure, but this is not very convenient since the numbering
is subject to change.

Is there an easy way to achieve rescaling of such Metapost figures?

Thanks,
Olivier