Hey, don't be angry, isn't that you've already write
the code above (post #807081)? and I've modified
your code above too. All you need is just do some
modifications.

Code:

---

if (mouse_right == 1)
{
   camera.y += mouse_force.x * 40 * time_step;
   camera.z += mouse_force.y * 40 * time_step;
}

if (mouse_right==1 && key_alt)
{
   camera.pan += mouse_force.x * 20 * time_step;// mouse movement changes PAN
   camera.tilt += mouse_force.y * 20 * time_step;// mouse movement changes TILT
}

---

That's it!