One thing you could do is collect together your points and then perform the statistical function on the collection. In the Signal Manipulation palette is the Collector Express VI. When you configure it, you will be allowed to enter the maximum number of samples to collect and it will create a single signal. The newest points will be added on the end and when the maximum is reached, it will act like a sliding window and drop off old points from the start of the signal when it adds new points to the end.
I hope that this helps, Bob Young
