getting argument from msxsl.exe into the stylesheet

I'm using msxsl.exe with the param=value and want to get this value in
my stylesheet to use it.

example:

msxsl.exe myfile.xml pretty_it.xsl param="2005-09-22" -o output.html

How do I do this? probably a simpel question (variable, param???) but no
luck.

thanks for any help

---Stuart