How to manually change the retention % in the Standard PO based AP invoice

Hi,

I tried to create an invoice with retention and came to know that the retention % is defaulted from the PO.
Is there any option to manually change the retention % in the Standard PO Based AP Invoice (not the Retainage release invoice).

For ex. In this business scenario we have created a partial invoice with retention (Invoice1), The supplier has already performed his obligation (Say achieving a benchmark or a deadline) due to which we would like to reduce to overall retention % in the subsequent invoice. But in the subsequent invoice the retention will be defaulted from the PO and we don't have an option to manually edit it. Also, if we adjust the retention by creating a change request in the PO, then it will not be reflected in the first invoice - Invoice1.