Thanks to Mark FX I got a other idea, sorry… but its so fun 
Lets make a mouse event to execute the screen saver…
The script need to be saved as applet and be running to work.
To test the script you move the mouse cursor to top right corner of your screen and wait 5 seconds.
And the screensaver will activate.
use framework "Foundation"
use framework "AppKit"
use scripting additions
on idle
my activateScreenSaverFromMouseEvent()
return 5
end idle
on activateScreenSaverFromMouseEvent()
-- Get the Screen size
set screens to current application's NSScreen's screens
set theScreen to (screens's objectAtIndex:0)'s frame() -- main screen
set {{x, y}, {width, height}} to {item 1 of theScreen, item 2 of theScreen}
-- Get the mouse location
set theLoc to current application's NSEvent's mouseLocation()
if ((theLoc's x as integer) > (width - 10) as integer) and ((theLoc's y as integer) ≥ (height - 10) as integer) as boolean then
tell application id "com.apple.ScreenSaver.Engine" to activate
else
return 0
end if
end activateScreenSaverFromMouseEvent