Add space after the Exercise environment

I can't figure out how to add a space (say 3em) after the Exercise environment . I don't want to do it manually for every exercise, but automatically, by using \addtolength or redefining the environment or something.

For leaving some space in front of it I managed to come up with this:

\renewcommand{\ExerciseHeader}{\vskip 3em\centerline{\textbf{\large\smallpencil
\ExerciseHeaderNB\ExerciseHeaderTitle%
\ExerciseHeaderDifficulty\ExerciseHe开发者_开发问答aderOrigin\medskip}}}

I suspect this one must be redefined

\def\endExerciseEnv{\termineliste{1}\@EndExeBox}

I tried to redefine it but it doesn't work

Thanks.

With support from #latex @ freenode.net, I found this hack:

\makeatletter\def\endExerciseEnv{\termineliste{1}\@EndExeBox\vskip3em}\makeatother

If anyone knows a clean way to solve it, feel free to post it.