Get a new ISP 😉
Unfortunately, without Crontab, you wont be able to do that without writing a daemon to do it for you. You can write one in PHP, but that takes a special build of the CGI version which, I highly doubt your rat-bastard hosts would even think of providing.
You could write one in perl though.
But, the easiest thing to do is find another host, one that treats you like a man.