Countdown timer with realtime on the fly updates

My budget is $30.00 for this project. Please do not bid more. I need to have a countdown timer created that can be run on a website. It should display minutes and seconds. I should be able to update the timer on-the-fly from one computer and all the people that are on that webpage will see the updated value. For example: 5 people are on page [login to view URL] The timer is counting down from 15m 30s I access the script from one computer and update the time to 30m 25s and all 5 people who are viewing the page now see the timer counting down from 30 minutes 25 seconds without refreshing the page. Here's some timers you can look at but they don't function exactly as described.