I've never done this but first though is to set all the indoor for a open iris shot, meaning very low watt bulbs and minimum fill to make the place look better lit on screen than it actually is. Bear in mind most parties I've been aren't well Lit inside, it tends to be more mood lighting.
Since you are shooting over the shoulder, you are presumeably still showing part of the room, so probably don't want to be changing exposure as this would show where the room is in the frame. This fixes your exposure at a wide open iris with possibly some gain to get anything at all to expose from the night city outside. You'll probably want to choose your location carefully to maximise the number of visible lights and lit windows outside, as these will be the only things visible. Or you could shoot at "magic hour" just as the sun sets or rises to get some light and colour in the sky as well.
Now you have your exposure level set, point your camera back inside the room and set all you room lights at appropriate levels to suit that exposure level. As Icarus2005 says, this will probably involve low wattage bulbs in light fittings that are in shot, and possibly neutral density "gels" in front of lamps to knock their level down (unless you want the very warm look that dimming lamps right down gives). :thumbsup:
