use r4 instead of r2, this is the latest version.
In r4 you can assign a key "lock current scene" in the options menu:
Settings --> keys --> assign a key --> choose a key --> scenes keys --> lock current scene
The easyest way to lock and choose scenes in r4 is by using the webinterface of r4:
in the r4 menu do following: settings --> network acces --> set "enable" on.
and then type in your internet explorer: http://localhost:8888/
in the lower left corner you can lock and unlock scenes.