How To partial pay an vendor invoice?

We have a ton of invoices in desk drawers because there are problems on the invoice or with a three or two way match.  In 90% of the cases the problem is only related to one line on the invoice ... not the entire invoice.  Accounting and Procurement has asked me how to only pay part of the invoice.  I can't seem to find anything on this in the manuals for ERP 8.0.  Here is a specific example.  Receiving receive 3 of the 4 lines on the invoice.  AP wants to pay the 3 lines, short paying the 4 since we have to do research on this.