# days in range of dates that includes some duplicates separated by two blank rows

I have a list of dates of customer purchase activity. I need a formula in column (J) that finds all dates that belong to a particular customer and figure out how many days since their previous order. The customers are separated by two blank rows. Each customer may have duplicate dates but I need to calculate since the last different date. Then I need to calculate the average from the range of those answers, (see the gray in the green columns). I don't know how to calculate if there is a different date, (from blank to blank). I manually did the first and last to show what I am trying to create. See attachment.

I don't see that the dates are sometimes text and sometimes actual date format.
The dates are always sorted in descending order.
I would prefer an Excel formula because I understand formulas better but a macro would be ok.

Thanks

Sorry but my excel sheet that I posted was the wrong one. Here is the correct spreadsheet.

The previous one had too many tabs and this one only has the correct spreadsheet. I created a video explanation. https://www.screencast.com/t/OlF4YmjJD6ic

Thanks, Carim, all the dates in column A seem to be FALSE or Text but I don't understand how that helps me with the original question.