How to run a process in the background

Hi
I have solution which has multiple app’s. I need to run a process constantly in the background that monitors for a specific table field condition to be met. Once met it should either open an app or display an image in the main app menu and ideally make an alarm sound. The user will be performing multiple operations while this process is running in the background

Example:
Table test1 has fields update_time and alert_time.
If update_time => alert_time alarm user (ie: launch app or show image in menu)

Please is there anyone who can advise hoow I would do this?

Thanks

Larry

If your program is running on a web browser
You need javascript to create a timer http://javascript.info/tutorial/settimeout-setinterval to execute AJAX request http://api.jquery.com/jquery.ajax/

If your program is running on server
You can use a cronjob to run a php script