insert a row every nth row and sum range

Can anyone help me create a macro that will insert a row every nth row and at the same time sum the values of the cells above it? I have a data sheet that has 240 values per day in three columns. I am looking to separate the days with a row that sums the totals for all three columns for the day. The values are based on 24 hours so I would also like to get a daily average by dividing the sums by 24 but if anyone could help me with just the first part it would be greatly appreciated. I have 25 years worth of data that must be broken down into months and I am working with hourly readings per day --very tedious without programming.
Thanks, barb

I would use SUMIF or SUMPRODUCT formulas, and put them _above_ all the data. They're easier to find.

If you post a sample of your data, I or someone else will show you how.