LookAt something while rotating on z?

How do you get an object to do a LookAt while enabling transform.rotate on its z? I just realized that using LookAt forces the y axis to look upward, disabling the possibility for rotating on the z axis. I need the object to to both at the same time in Update.

Thanks

LookAt has an optional 2nd parm for the local y-axis, which merely defaults to world-Y. To sort of preserve the current up, could do:

Vector3 oldY = transform.up;
transform.LookAt(target, oldY);