Run code multiple times

Hi.
In this workbook Test1.xlsm under column "D" i have Po numbers. Some PO numbers are the same and some aren't. I have a specific code that creates an invoice for a customer when i hit the code however i must select a cell under column "D" in order for the code to create an invoice for the customer on that row. I usually create the invoice for all the customers of the same PO number. Sometimes the amount of invoices i have to create is overwhelming so i was wondering if it's possible that when i select a cell under column "D" that has, let's say, PO number "654" if the code can create an invoice for all customers that have the same PO number of "654"?

Where's the macro?