[Grml] grml-live, specifying GRML_LIVE_SOURCES

[T o n g]

Hi,

Is it possible to *add to* current GRML_LIVE_SOURCES setting? 

I tried, 

GRML_LIVE_SOURCES="$GRML_LIVE_SOURCES
# debian multimedia
deb http://www.debian-multimedia.org sid main non-free
. . .
"

but got 

 /etc/grml/grml-live.local: line 29: GRML_LIVE_SOURCES: unbound variable

then I realized that the grml-live.local should be in python syntax, 
which I don't know. 

Please help. 
Thanks