A macro for a excel file

I am not sure if this is possible to do but wondered if you may be able to help.

We have listings on eBay , each listing has a listing number and a custom label number.

We need to update our stock on a daily basis by creating a excel file.

The problem is we have to use the eBay listing number to update the stock but the report we get from our supplier only gives the custom label number.

I have attached a sample Ebay update file and a sample stock file.

Is there a way of updating the sample eBay file using the stock file by excel searching for the custom label numbers and then updating the stock quantity, perhaps some kind of macro ?

I hope you can understand my rambling ! LOL as I realise its a bit difficult to explain.

Many Thanks