yep easy to do - I call it the travelling mean :)
Note you will need to keep track of the 1. 'count' of values, 2. previous 'mean' and 3. the 'new value'. Algorithm is:
in words : ('previous mean' * '(count -1)') +'new value') / 'count'
benefit you have a running mean can do the same with 'standard deviation' just a little more complex
