Using a custom solver


I am new to Unreal engine 4 and I am doing the following : I have a custom C++ constraints solver library I want to use in Unreal.

I would like that when I drag an actor in the viewport, I have a callback to call the custom constraint solver which would update the matrices of actors in the scene.
Can you advise me on how to do this ? Do I need a C++ plugin, if so, what kind of class ? Or can I do it directly with Blueprint ?
Thank you.