Compare fields in Different tables

I need to make a list of all purchase invoice lines where the purchase amount is different from the sales amount.

I have added a field that connects the Purchase Invoice Line to the Sales Invoice Line, we call it the Hog Ledger number. For each Hog Ledger entry, there is one Purchase Invoice Line and one Sales Invoice Line.

So, i need to create a list of all Purchase Invoice Lines, by Hog Ledger Number where tha Amount is different from the Sales Invoice Line Amount.