I am using vixie cron, but I've just noticed that that piece from the manpage is under the heading "debian specific", so it is probably a custom mod. Sorry guys. As a more generic solution, try this:
Code:
echo -e "`crontab -l | tail -n +4`\n5 * * * * /path/to/your/cron.job" | crontab -
This will trim the first 3 lines from the output of crontab -l.