how to make crontab to work debian lenny

just add the following line:
10 18 * * * export DISPLAY=:0 && vlc /root/Desktop/playlist1
vlc /root/Desktop/playlist1 is an example of job to start
the command you want is after the "&&"

without the command: "export DISPLAY=:0" cron isn't working

to stop the process:
10 22 * * * export DISPLAY=:0 && pkill vlc

good luck!
p.s. editing crontab: debian:~# crontab -e
viewing it: debian:~# crontab -l