Duplicating info in another worksheet

I have a worksheet with a column of PO #'s. Because the PO is not always paid at once, I may need to enter the PO # in a row more than once to capture the amount(s) paid. I'm trying to keep a running total of the PO amt on a separate sheet.

How can I get the PO # to transfer to the total worksheet when I enter it into the main sheet without duplicating the number?