I'm not sure that that helps - I want to define an action in the exact moment when I release a button.
That shouldn't be hard to implement. You just save the current state you're interested in. I haven't worked with control state, but I don't see, why it shouldn't work:
Start of layout
->SomeVar = "Released"
System: MouseKeyboard.ControlState("Move Left", 1) Equal to 1
SomeVar Equal to "Released"
->SomeVar = "Pressed"
System: MouseKeyboard.ControlState("Move Left", 1) Equal to 0
SomeVar Equal to "Pressed"
->SomeVar = "Released"
->do stuff
(Maybe 'trigger once' will do as well instead)