Microsoft Excel 2010, input file of thousands of rows of hourly data, thus there are 24 values (rows) per day.

Let's assume that my data starts at B1, and let's assume that I put my average value for Day 1 into C1. The content of the C1 cell will be =AVERAGE(A1:A24), so far so good.

The question is what do I need to put into the C2 cell to make it so that the content of the C2 cell will become the average of A:25 through A:48 in such a way that I can copy the same formula down the C column and it appropriately fills in C3 as average of A:49 through A:72 and so on?