Update pricing and mark discontinued items for master price list

I've got 2 sheets.

First sheet is my own master price list.
Second one is Supplier "Fruit Co." price list.
Third one is Supplier "Produce Land" price list

Every year the supplier's will change their price list. Sometimes they will add items, sometimes they will remove some and sometimes they will change the pricing.

I only have 1 sheet for each supplier, so if the supplier introduces a new price list, I clear their current one and paste in the new one. The formatting remains each time.

I would like to rig something so that if the master file has the same part number and supplier as another sheet, it will look to see if the cost price has changed, and if it did, the it will change the price on the master file.

Also, if the product is NOT to be found on any of the sheets, then the product will be marked "disco" followed by the year indicated in the spreadsheet's effective date column.

Only problem, my actual sheet (this is just an example) is uber complex and has a crazy VBA running in the background. I was hoping to use vlookup in the master file's cost column and disco column to update it, rather than VBA.

Is someone able to rig the example spreadsheet to work so I can try and apply the changes to my ultra complex one? (hope my attachment worked?)

Thanks!