Excel 2003 :: Copying First Instance To New Worksheet Then Adding Total Units?

Basically the first worksheet (equipment list) is set out for parts used for each individual unit which can be printed out for each unit.

The second worksheet is an equipment list, where each part number and quantity required is displayed which can be sent to suppliers for ordering.

At the moment I

-> copy the equipment list to a new worksheet
-> do an advanced filter for "Unique records only"
-> =SUMIF('Equipment List'!B:B,'Parts List'!A16,'Equipment List'!D:D)

which is much faster than the way we used to do it.

The problem is, when I add a part to the equipment list that is new, I need to go through the process again.

Is there a way to automate so any parts I add to the equipment list, if it is the first time the part number has been entered, it will copy to the parts list worksheet and update the qty column or if it is an existing part number it just updates the qty column?

The equipment list may potentially have up to 100 different drives, but using mainly the same equipment.

I created this sample on an old desktop using excel 2003 but I use 2010 on my laptop.