to have a script that turns off your projectors, best would be to write your own windows batch file.
In the StageDesigner program folder under tools/pjlink you find a tool named pjlink_interface_windows.exe.
copy it along with the dll to a folder
inside this folder, create a textfile and name it turn_off.bat
pjlink_interface_windows.exe --power off --beamer 10.0.0.1
Then double click the turn_off.bat file, it should turn off the beamer with IP 10.0.0.1. Inside the program folder is also a PJLink emulator, it may help you.