Set the axis of the Bone to Modify to point towards the Look at Target. A value of 1 will enable the axis to be factored, a value of 0 will disable the axis to be factored. A value set of (0, 0, 0) will allow a default axis to be used. You can also enable the axis to be factored in local space by enabling the Local Space property. When the Local Space property is disabled, the axis will be factored in world space.