Associate Identifier with Pledge

I need to associate a unique ID with each new pledge via API. That is to say, when someone clicks the button on our site to make a pledge, they will have to enter their avatar’s name and click continue. I need a method of reconciling the avatar name with the pledge ID. If this isn’t possible I will have to look for another service as you are not integrated with our end user platform and privileges will have to be upgraded manually.