I don't think I explained it well. It doesn't matter if it's mouse/keyboard/button.
In this example you'll agree that var will be 0 every tick regardless of whether it starts as 1 or 0:
<img src="https://dl.dropbox.com/u/8367729/construct/pics/var1.png" border="0" />
This is the same thing only when space is pressed:
<img src="https://dl.dropbox.com/u/8367729/construct/pics/var2.png" border="0" />
var will always be 0 because if the first event makes it 1 then the second event will set it back to 0.