Macro to run formula based on a range of data in some rows of a column

I need to develop code for a macro (or better yet a private sub that does it all):
Sample sheet attached.

Some background.

Rows are grouped (I have colored the groups to aid in understanding) by the value in Column E. (Tag 1). Each group can have from 1 to 8 duplicate values (Duplicate tag 1’s)

What I am trying to do is create some formulas in Columns O,P,Q&R ON THE LAST ROW OF DATA FOR THAT TAG1). (real life examples are located in Row 2)

For example: In Column O, I want to add the values for M for only those rows with that group’s tag number.

I have manually inserted formulas in Cells O3,O10,015,019 &O21 just to demonstrate how I would like things to look in that particular column when I am done.

It seems to me that the logic might be Keep track of the count of row E until the value changes to a non-duplicate and then use the result of that count to define the # rows in Column M to sum and display in the appropriate cell in Column O. A mouthful that is well beyond my level of expertise.

Any suggestions would be greatly appreciated.