Input.GetAxisRaw might be what you're looking for. In the Input Manager (Edit -> Project Settings -> Input) setup a variable for "Mouse X" and "Mouse Y" (if not already setup [as below]).

Then in code;

Vector2 mouseMovement = new Vector2(Input.GetAxisRaw("Mouse Y"),
                                    Input.GetAxisRaw("Mouse X"));

And use that for the rotation of your transform. Hope this helped.

Input.GetAxisRaw might be what you're looking for. In the Input Manager (Edit -> Project Settings -> Input) setup a variable for "Mouse X" and "Mouse Y" (if not already setup [as below]).

Then in code;

public class CameraMove : MonoBehaviour
{
    private Vector2 pos;
    private bool    isPanning;

    public void Start()
    {
        pos = new Vector2();
    }

    void Update()
    {
        if (Input.GetMouseButtonDown(1))
            isPanning = true;

        if (Input.GetMouseButtonUp(1))
            isPanning = false;

        if (isPanning)
        {
            pos.Set(Input.GetAxisRaw("Mouse X"), -Input.GetAxisRaw("Mouse Y"));
            transform.Translate(pos, Space.World);
        }
    }
}

For movement in the Y plane, the value from the mouse must be negated to, unless you with to use inverted controls. Hope this helped.