1. I want to turn off screen at any time.
    > xset dpms force standby
  2. I want to assign a key shortcut to the command (taken from here).
    1) alt+F2 to open up a run prompt
    2) type gconf-editor
    3) go into apps > metacity > global_keybindings
    4) select one of the run_command_# and type your desired key stroke..so you can just type «F12″ to set the command to F12.
    5) now go back one level and go to keybinding_commands
    6) find the command_# from step 4 and type kill -9 $(ps -C amule -o pid=) or whatever you want the command to be