[pstricks] conditional graphics

[piatecki]

I am writting a course and I want that some graphics appears in the text 
I give to my collegues but not in the text I give to my students.

I am thinking of a command which take a general boolean parameter 
defined in the preambula and wich will be interpreted as the 
verbatim.sty command

\begin{comment}                           %\begin{comment}
                                            or
\end{comment}                               %\end{comment}

according to the value of the general parameter.

I have tried to do this with ifhen.sty and other package which implement 
conditionals but, obviously, It doesn't work. Does somebody has an idea ?

Thanks

Cyrille Piatecki