\begin{saveblock}{codebox}
	\begin{highlightblock}[linewidth=0.4\textwidth]
		% File: bibfile.bib
		@article {...
			...
		}
	
		@book {...
			...
		}
		...
	\end{highlightblock}
\end{saveblock}

\begin{saveblock}{codeboxB}
	\begin{highlightblock}[linewidth=0.6\textwidth]
		% File: document.tex
		\documentclass[a4paper]{article}
		\usepackage{biblatex}
		\addbibresource{bibfile.bib}
		
		\begin{document}
			This has been shown.
			\parencite{babington}

			\printbibliography
		\end{document}
	\end{highlightblock}
\end{saveblock}

\begin{frame}{Minimum working example (biblatex met backend biber)}
	% Je hebt dus twee bestanden, die er minimaal zo uitzien.
	% (voor biblatex met backend biber)
	
	\bigskip\medskip
	\begin{columns}
		\begin{column}{0.4\textwidth}
			\useblock{codebox}
		\end{column}%
		\begin{column}{0.6\textwidth}
			\useblock{codeboxB}
		\end{column}
	\end{columns}
\end{frame}