*The source file for the pivot tables is updated
on a weekly basis. *

How do you update the source file?
Is the source file and Excel document?

There are hundreds of parts and several
are added weekly, but I only need the data on a specific
12 or so parts. *Whenever I refresh my pivot tables I get
these new parts that I don't want. *I have to manually remove
them from the column fields. *

How do you decide which ones to remove?

I was wondering if there was
anyway to "fix" the column fields so that this manual function
was no longer necessary?

It's difficult to say without seeing some kind of sample.