andrew kramer day2night- possible to add mask to car lights?

hello,

Im trying to achieve a similar effect to that of andrew kramers day2night, where he adds lights to moving car. The problem im facing is that the car drives through the view of an alleyway...meaning it appears from left and then disappears to the right... Ive been trying to add masks to the lights layer so that they cant pass the part where there are walls, but the masks dont actually affect the spotlight effect.

Any way around this?


thanks in advance!!

thanx for the help.