Rolling 24-month Averaging

[1brickshy]

One of our govt. agencies requires that I compute the 24-month rolling averages of the daily average input to a manufacturing process. In this instance, the agency is demanding the rolling average since 2003, so there are a fair number of data points involved. The process control computer can provide me the daily data (attached file contains 30 months of data), but cannot compute the 24-month rolling average and nothing in the Excel HELP feature helps!
Thanks. 1brickshy