Is there a way to automatically compute averages of groups of data in a single column?

I have about 90 data files exported from a laboratory apparatus. Each of these data files has a single column of data (usually about 1000 "rows") spread across three groups. These groups are separated from each other by blank cells and are of varying size. Is there any way to automatically compute averages of these three groups and put those average values into their own cells at the top of the spreadsheet? I don't need them to be named or anything, I can do that myself after the averages are computed since the groups are always in the same order. Basically I need a formula/function/macro that will select data ranges in a single column based on separation by blank rows and put their averages into easily-accessible cells. Thanks in advance.

Sure, I added an attachment to the first post.