Using VLOOKUP across two sheets with multiple matches

I have two separate spreadsheets.
Sheet 1 has a product ID, Description and Barcode. The Cost column is empty and it is this that I am trying to fill from sheet 2.
Sheet 2 Product ID, Description and Cost.
As you can see, there are multiple lines with the same Product ID and description, but different barcode - these represent different sizes/colours etc. but they all cost the same.
So how do I fill column "D" - the Cost in sheet 1 from column "C" - the Cost in sheet 2?
I have assumed it is a VLOOKUP, but maybe something else altogether... Warning - I am an excel novice....