Total for Cells with same name value
 

I am sure I've done this before. somehow it alludes me all of a sudden;

I have a table with

ProductName | Amount Sold

Where Product Names can duplicate

Sorted by product name

I want to run a simple column formula so it will step down and as long as it
is still in same product group (i.e. A6=A5) it will give me a report on the
totals.