How to find duplicate invoices when the duplicate may contain a letter?

Hmm, this isn't doing as much as I thought it would.

Might have to start over here. Currently I have a pivot table with the following information.

Vendor Invoice# GL Account Total

How would I find duplicate invoices here, even if the invoice may contain an extra letter?

Would I find just use a countif formula to find duplicates of invoice, gl account, total, and one that runs to see if there is an invoice with an extra letter?

After this is done and say I want to pull out entries that have duplicates of invoice, gl account and total, how would I do that?