How do I get the bone rotation of a Mesh before Transform (Modify) Bone's changes?

I’d like to rotate bones of my Skeletal Mesh dynamically, depending on the original rotation of a bone.

To get the bone rotation, I use Get Socket Transform > Break Transform, or Get Socket Rotation.

To add to the bone rotation, I use Transform (Modify) Bone, with the rotation mode Add to Existing.

The issue is that both “get” functions return modified rotation values, while Transform (Modify) Bone works on the unmodified rotation values.

For example, say I have an animation that has a rotation of 150 for a certain bone, and I’m going to apply a constant roll of -90 to that bone.

On the first frame, it’ll rotate the bone 150 + -90 => 60. Then on the second frame, it’ll do the same rotation the bone, 150 + -90 => 60.

But when it comes to the “get” functions, they’ll both read 60, the post-modification values, instead of 150 which I need.