How to do relativte offset rotation

I have two rotations in the form of vectors, in the start function I want to save the rotational offset between the vectors. The first vector is going to be the reference vector that a will use to get the second right. So I want to be able to keep the rotational offset between them during runtime

Don't know if I made it clear enough, hope you understand.

T$$anonymous$$s is want i have tried:

 void Start ()
 {
     avgFixerDir = xxx; //the on that will be correct during the runtime
     mRotationOffset.SetFromToRotation(avgFixerDir.normalized, transform.forward);
 }
 
 voud Update()
 {
     newForward = (mRotationOffset * avgFixerDir.normalized); //trying to get forward to the same ralative offset as in the start
 }