I am wondering how to get the current local rotation of a transform around a specified axis.

For example you can rotate an object around an axis with the following:

this.transform.Rotate (Vector3.up, 0.5f, Space.Self);

What I would like is an inverse function of this so I can get the amount rotated on this axis, eulerAngles or localEulerAngles wont return this. So for the case of running this function 10 times the expected result for rotation in the axis Vector3.up would be 50f