Help with cron job

Hi all I have become a little unstuck trying to use cron to run a PHP script on a regular basis. A programmer I know did the script for me and I haven't a clue how to change it to what I want. Basically I am looking for a job which will run every three hours. The programmer did the following: * */3 * * * /usr/local/bin/wget -o /dev/null -O - http://mysite.com/look_csv.wow > /dev/null and my email tells me that this script is running more than once a minute :) I seem to have quite a lot of emails coming in from the confirmation that this script generates! Any help would be appreciated here as to what I've got to change to get this right Thanks ade