How to add payment refund service

[Vamsi]

hi,

                 I have wriiten my own payment refund service. I made in
entry in the service as well and created a service extending
paymentRefundInterface.
How to call the refund service?
 where actually it should be called I want to refund a Order
I am little bit confused that is I need to provide extra screen for this
refund or is ofbiz provides any thing like this .

regards
Vamsi