Set bone rotation?

I hope there is no stupid question…

I have tried to update the rotation value (BMM_additive) of a bone from the HeroTPP skeletonmesh at each frame. But the bone moves only once when I simulate or play the animation in the Animation Blueprint previewer.

Could somebody tell me how to ask to the engine to rotate a bone by a precise angle in a precise time interval? Or on a frame basis?

Thanks a lot!