There's a Volvo wrench extension tool that is used for that same purpose, so yes you can do that, as long as whatever you end up using will fit inside the crank locking tool. Volvo's "multiplier" is just a wrench extension bar, you set your torque wrench to ~255lbs and it ends up at ~340 on the end. If you have something that will achieve the same effect, I don't see any reason not to use it.
