How to trigger secondary http in partner profile

I have an existing trading partner profile where the primary http in the delivery method has been configured to a particular URL, e.g. A, and checked as the “preferred protocol”.

Due to a new conversation script for another purpose, we need to send some other document (while old one still using A) using a new URL, e.g. B, for this same partner. How can i trigger the secondary http instead of the “preferred protocol” in this case.

My first thought was to change the service, wm.ip.cm.handlers:send. And change the triggering B2B service in the conversation script for the “Send Document” step.

Does anyone has any experience to pin down the exact service or sub-service to modify. Appreciate any advise.