Running a cron job manually?

[Michael Hipp]

Does anyone know a way to force cron to run a job manually?

Explanation: I need to test cron jobs. Obviously I can run the job from 
the command line, but it generally has a very different operating 
environment than what it has when run by cron. Constantly changing the 
time in crontab is a pain as I need to do this over and over for 
testing. Is there some way to say "Hey, cron, run the job listed on line 
twelve!"

Thanks,
Michael