So, what you are trying to tell me to try whether the interrupt works or not?
Similiar to this example: http://www.dave-auld.net/index.php?option=com_content&view=article&id=107:arduino-interrupts&catid=53:arduino-input-output-basics&Itemid=107
Yes, same principle. Just put the code to turn the LED on in the function that you want to check is executing.