Azure - queueing time based tasks
You need to use a scheduled task. There are two good libraries out there that you could use:Quartz.Net andCastle scheduler.
With a scheduledler, such a task becomes easy.You just create a job that runs when the processing time expires. There you would check for any unprocessed requests and if there are any left, you notify the next set of people and set another scheduled start to fire after processing time expires.
Let me know if you need further detail.
I've used Quartz.net in an azure webrole successfully in a production app.