if you're only wanting to call the function when you press the button, an event listener shouldn't be needed.... That is if you button is calling code when it is pressed.
If you simply remove the eventListener, and the e:Event it should work. The following code will call the function when loop(); is called. So if you wish to execute the loop function from the button code, place loop(); in the call.
Note the function isn't required to run from an eventListener.
if(con.rotationY > 90 && con.rotationY < 270)