No thoughts about the "something" prohibiting you from attaching the sample, until you describe in more detail. What exactly prohibits you? What are the symptoms? Do you fall ill every time you try? Does the IRS spring an audit on you, thus distracting you? Or (just guessing here) do you get some kind of error message, and if so, what does it say?

Meanwhile this doesn't sound too hard. I expect you're adding new shifts by typing in a new row at the bottom of a worksheet or inserting a new one at the top, right? If the latter, you want a formula that will average one of the columns in the top 30 rows—data rows, excluding the worksheet headers if any—but a formula that at the same time won't "follow" the data down as you insert new rows.

If you want the bottom 30 rows, I'm sure it's almost as easy but I'm thinking about how to spot the last row in a formula. Of course you can write a worksheet function of your own to do this, but it oughta be easy enough using just standard worksheet formulae.