First of all. What OS you have? If its *NIX then you use Cron for the job. Unfortunately I havent used it so I dont know how to set it up.
If you have a windows-server, then you use the task scheduler which comes with Windoze. You just add a new task for the scheduler. For example:
C:\PHP\php.exe C:\apache\Apache2\htdocs\dascript.php
To set the interval for it, click 'Advanced' in the Schedule-tab. There you can find 'Repeat task' where you can set it to run every 60 seconds.