How do I make a more sophisticated "Roller"?

How do I make a more sophisticated "Roller"?

I am looking for a good example of a percentage roller in Silverlight. (someone told me that they were called rollers)

The little default BusyIndicator is nice but I have a lot going on in the backgroud for a particular app and because of this, I want one of those rollers that give a percentage of how much time the use can expect to wait. I already have a way of determining what sort of percentage is going on. In other words, I know what sort of data to send the roller. Can anyone help me?