Eliminate duplicate values

I have attached a snapshot of a big spreadsheet to explain my query. There are duplicate customers shaded with colours (Column D) with different Asset Type (Column G). I need to have one Sales Value for each Customer. That means values in Sales (Column I) would look like those in Column J.

Is there any shortcut way to eliminate the Sales Values for duplicate Customers? I need to copy that across the big spreadsheet, a part of which is attached herewith.

Thanks for any help. Regards.