Thread: Summing rows if data in column A matches

OK, my first post and I'm going to let you know I'm not all that good with Excel. I can do some stuff, but it's not my forte.
I have a report at work that for whatever reason lists multiple rows for the same item number. What I need to do is compare the item number in row A. If they match, then I need to add (sum) column N - AF for the two matching rows.
My biggest problem that I see is that I don't know how to put the code in for a range of rows that compares each cell in column A to see if they match. I have attached the .xlsx so you can see exactly what I'm referring to. Some of the amounts and/or values have changed for work purposes. I haven't added any code to my post, because I don't really even know where to start. Also, after looking around for a bit, I didn't see any posts that addressed my specific needs.
Thanks in advance!

Maybe I didn't give enough information. First, I need to compare the value in A4 to every other value in column A. If they match, I need to add the values in the matching row from column N to column AF. If they don't match, I need to move down to the next row in column A to see if that value matches any of the others, in a loop until finished. My problem is, I don't know what command (or commands) to use for a macro, and I don't have the skill to try to write the code for it. Can someone at least point me in the right direction for what I'm looking for?