Customising counter within enumerate-list

Question

Please consider the following code. I would like to use the enumerate-environment to generate a list, which (for better understanding) I built with the tabular-environment. I would like to have the second item labeled as "2-5.".

\documentclass[fontsize=12pt, paper=a4]{scrartcl}

\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{ngerman}

\begin{document}


\begin{enumerate}
\item bla
\item bla bla
\item bla bla bla
\end{enumerate}


\begin{table}[htbp]
   \begin{tabular}{rl}
1. & bla \\
2-5. & bla bla   \\
6. & bla bla bla  \\
   \end{tabular}
\end{table}

\end{document}  

Answer 1

If you want to resume the numbering after a modification

\documentclass[fontsize=12pt, paper=a4]{scrartcl}

\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{ngerman}

\begin{document}
\begin{enumerate}
\item bla \stepcounter{enumi}
\item[\theenumi--5.] bla bla \setcounter{enumi}{5}
\item bla bla bla
\end{enumerate}
\end{document}

Thanks to egreg and Mico for the correction/modification!

Answer 2

I think you are looking for the optional argument to \item:

\documentclass[fontsize=12pt, paper=a4]{scrartcl}

\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}


\begin{document}


\begin{enumerate}
\item bla
\item[2--5.]\addtocounter{enumi}{4} bla bla
\item bla bla bla
\end{enumerate}


\begin{table}[htbp]
   \begin{tabular}{rl}
1. & bla \\
2-5. & bla bla   \\
6. & bla bla bla  \\
   \end{tabular}
\end{table}

\end{document}