Partner Program - logging partial pay-outs to Partners

Right now we can only press one button to 'pay partner' which will pay out all commissions currently in their Partner record. I want an option to 'partially' pay out these commissions, and select the exact purchases to pay out the Partner for.

We are trying to do a 'true up' now that the Partner Centre has been improved and some commissions have been physically paid, and some have not, so I want to be able to show an accurate representation, without having to pay out all unpaid balances.