\startex
\dontleavehmode\beginvtop
% to remove the overfull \hbox message reduce \hsize with
% the width and distance values of the enumeration
% \hsize\dimexpr\textwidth-2em\relax
\startitemize[joinedup]
\startitem First \stopitem
\startitem Second \stopitem
\startitem Third \stopitem
\stopitemize
\endvtop
\stopex