How to ignore already running task in Windows Service running at 3 Minute Interval

Hi ,

I have created an windows service which is running at every 3 minute interval on which i am doing some data manipulation task, suppose a task is taking more than 3 minutes and service restarts again then the already going on task stopped and starts again. is there any way to ignore the already going task.

Kindly share some examples.

thanks
vinay