Variable numbers of rows, multiple columns (some blank cells): require summation based on values in cells in one column

[AdamBB]

I am working on geological borehole log data, with a set group of geological units being repeated down the column D. However, We have defined "sequences" based on specific depositional times and environments (column E).

 

[AdamBB]

So embarassing! I posted this before I had finished writing it, and can't see how to delete it.

I will complete the question and post ASAP.