having Shading/unshading function only for one specific application window with xfce

[Yves Perez]

Hi everyone,
I've just started using xfce/xfwm4 and quite happy with it.
I would be fully satisfied if i could do this :
I would like the behaviour of shading/unshading windows working only for 
one of my X client application (written in perl/Tk/Zinc) ... and not the 
others.
It doesn't seem possible when reading the xfce 4 window manager man page 
...  Is this right ?

Thank you.