Slerp in Worldspace, script problem

Hey guys,
I just want to rotate in worldspace instead of an object´s local space. Here is thre line that actually moves it in local space. :

Code (csharp):

1. transform.rotation = Quaternion.Slerp(transform.rotation,desiredrot, Time.deltaTime * turnsmooth);

"desiredrot" is specified some line above in this way:

Code (csharp):

1.         xangle=transform.rotation.eulerAngles.x;
2.         yangle=transform.rotation.eulerAngles.y;
3.         float tiltAroundY = Input.GetAxis ("Horizontal") * turningspeed+yangle;
4.         float tiltAroundX = Input.GetAxis ("Vertical") * turningspeed+xangle;
5.         float tiltz = Input.GetAxis ("Horizontal") * (-bankamount);
6.         Quaternion desiredrot = Quaternion.Euler (tiltAroundX, tiltAroundY, tiltz+desiredzrot);

So, do you know how I can make this object rotate in worldspace instead of it´s local space?

Thanks, Mike