First, i don't think your host provider would accept this. Second, to answer you question you can make a cron that runs let's say every minute and in the script you can add a code that recalls your file every x seconds, but be careful no to start more loops, i managed to do this creating also a script that kills the previous cron (that was run the previous minute), or you can think to something similar.
As asdirc said the host provider may not allow you to run a cron job or even if they allow they may want to know the purpose and frequency of the job. So just check with them before going ahead. Now if they are happy and you are ready then you can do the following (steps using hostgator cpanel): 1. login to your control panel 2. Go to the last section called Advanced 3. Click on Cron Jobs 4. Select timing as appropriate and give your file which you want to run. hope this helps
You should ask your provider first. Becuse if you want to run the job every xx secs and the job is resource consuming then they will want to know more detail. Also Cron jobs are usually create by super users and i believe they run using that users privileges...but not sure about that. If that is the case, then I am sure hosting provider will ask questions.