Hello tperez,
In order to use change detection you need a hardware timed (correlated) digital input card. The NI 9425 is software timed (static) so change detection is not supported in your current setup. For a list of the correlated digital input cDAQ cards please see this article. You need one of the cards from the Digital section where the "type" column is correlated and the description column is "DI" or "DIO" All of these boards will support change detection.
If you'd like to speak with a technical representative at National Instruments prior to getting one of these cards you use the contact information at www.ni.com/contact.
I hope this helps and have a great day!
Brooks
