Creating New Files

Let's say we have 3 vendors that have large pricing spreadsheets.
Vendor A has 40,000 items
Vendor B has 35,000 items
Vendor C has 30,000 items
Approximately 75% of Vendor B and Vendor C's pricing spreadsheets contain duplicative item #'s found on Vendor A's spreadsheet. How can we create formulas that separate out the non-duplicative items on Vendor B and C's pricing spreadsheets as well as copies over all the corresponding data for each of those non-duplicative items?