How can I do the following:

I have a vendor who sends me price updates in msexcel of
about 10,000 items. The vendor's list of items is always
growing so there are new items inserted between rows on
updated lists.
I wish to maintain a list (subset) of say 1000 of these
items and do the following:
Match the rows, show price difference, create a
new list of the same 1000 items with the updated prices.