\enabletrackers[met*textex*]

\starttext

    \startMPcalculation
        path PicX ; PicX := boundingbox textext("?") ;
    \stopMPcalculation

    \startMPpage
        picture PicA ; PicA := textext("*");
        picture PicB ; PicB := textext("?");

        numeric Step ; Step := 10cm div bbwidth(PicX) ;
    %   numeric Step ; Step := 10cm div bbwidth(Xpic)  ;

        for i = 1 upto Step :
            draw PicB shifted (i*cm,0) ;
        endfor ;
        draw PicA ;
    \stopMPpage

\stoptext

