[NTG-context] Create an item marker with a counter with Metapost

Hi, With the book Metafun I created a marker with metapost. How to add a counter ? Best regards, Fabrice \startuseMPgraphic{itemize:fuzzy} numeric u; u:=0.5cm; save p; path p; p := fullcircle xyscaled (u,u) randomized 2pt; pickup pencircle scaled 1pt; fill p withcolor green; draw p withcolor blue; \stopuseMPgraphic \definesymbol[itemize:fuzzy][\useMPgraphic{itemize:fuzzy}] \setupitemize[1][symbol=itemize:fuzzy] \starttext \startitemize \item \input knuth \item \input knuth \stopitemize \stoptext