Most cars (Volvo included) have a lock/release button on drivers' door. If you can wedge the window frame out far enough to poke a coathanger (or something stiff but soft) far enough through the gap to push the button - that's usually how the roadside service guys do it.
The Vic guy had a pump up balloon (like taking your blood pressure) to wedge the frame/glass without damage. No personal experience, of course...bloody hire car...