[CM] how to set the working directory in grace?

[Michael Winkler]

Hi List

How can I set my working directory by code?

(set-working-directory! "/users/michael/Desktop") gives me an Error: 
set-working-directory! unbound variable

If I just open grace, there is no working directory by default, so I 
would like to make a load-file with, amongst others, this command.

best,
Michael

OSX 10.10.3, Common Music 3.9.0