\newcounter{nbrep}
\newcommand{\repete}[2]{
\setcounter{nbrep}{0}\noindent
\whiledo{\value{nbrep}<#1}{#2\stepcounter{nbrep}}}

\repete{3}{Hélas ! }




! Undefined control sequence.
\repete ...etcounter {nbrep}{0}\noindent \whiledo
                                                  {\value {nbrep}<#1}{#2\ste...
l.8 \repete{3}{Hélas ! }

? x