delete duplicated rows based on a criteria in another column

hi i need a macro that will delete all duplicated data in column A AND is blank in column F and then add the data in column AB..


Column A contains the order number...
Colunm F contains reference number...
Column AB contains number of pcs

What I need is that when there are the same order number with blank reference number, the number of pieces will be added into one cell..

confusing? i know.. in the attached is an example...

in column A there is 8 rows with the same order number and column F is all blanks... what i need is just to create this in one line and column AB will be the total of the 8 rows.

all these logic will be applied to all the same data in column A and with blank cells in column F. in my attached file there is a before and after sheet.. i have highlighted the outcome that i wanted.


I hope somebody could help me on this