Countdown Timer

We currently have a website which provides sports scores. The website shows the amount of time a game is in progress. This is based on an xml feed which we get from an external source. When the game starts the xml feed changes the status to "first half" and the time it started. We want a timer to start and after 1 minute show the word 1 minute and keep going every minute until xml feed status changes to "half time". When it reaches "half time" the timer stops but remembers the time e.g. 45 minutes and then when the xml feed status changes to "second half" it starts counting again. When the xml feed status changes to "finished" the counter will stop. We currently have a javascript program doing this but it slows the site down as javascript cannot run events simultaneously and if it does when you have 200 live games the site almost crashes. This we dont want.