Find highest rev number in one column of item number in another column and add total

Hello,

I am trying to find a way to find the highest revision (column 3) for each unique item number in column 9 and delete all the 'fluff".
I am also looking to add total to 'POLI_QTY' that captures the totals of all the previous PO_SUPP quantities, while maintaining the deletion of of the oldest PO_SUPP revisions.
For example, after the code is run, for S4540539, only PO_SUPP 4 is showing, but a total qty ordered of 81.3

Thanks in advance