First of all thank you to all of you who aswered. My test command works now,
so the days of stuff like \def\mymacro#1#2#3... are counted :)
I still have problems changing from \xdescgetparameters to the 
\rawgetparameters
command (I'll try to fix this later).

Regards,

  Peter


P.S.: my grep version is 2.4.2 ;)