Yes there is a way to lock the crank, but you don't have to do that when doing the timing belt. If the cams are locked, the crank pulley isn't gonna turn, if it does... then your tool broke and possibly the cams will be damaged.... And don't listen to what any normal mechanic tells you about modifications (especially on newer cars). Adjustable cam gears are fine (when installed properly) and don't do anything other than change valve timing.
