Issue refund but also refund return shipping

[bmwallpart]

A customer returned an item worth $75 and the original shipping was $25 so the total of the transaction was $100.

The wanted to return the item for a refund so they paid the postage (another $25).

I agreed to pay the return postage so now I owe them $125 total.

However; PayPal will not allow me to exceed the original total of $100 when issuing a refund.

Is it possible to include the return shipping $25  and refund a total of $125?

Please let me know how.