How to trigger a callback function in a GUI by a digital input signal (instead of mouse click/position)?

I want to build a GUI for instrument control and data acquisition ("event-driven programming").

When running the GUI Matlab continuously checks if certain user-defined "events" happen, e.g. "mouse click in region ..." or "mouse pointer is over region ..." and calls a user-defined callback function when such events occur.

I have a digital input signal (accessed via readDigitalPin(a,pin), where a is an arduino object), and I want to execute a certain callback function when this input goes from Low to High or vice versa.

How can I make Matlab "continuously" listen to this input (as for the mouse position/click)?

From

http://ch.mathworks.com/help/matlab/creating_guis/how-does-a-gui-work.html?refresh=true

"In the case of MATLAB UIs, most events are user interactions with the UI, but the UI can respond to other kinds of events as well , for example, the creation of a file or connecting a device to the computer."

I conclude that this functionality is available but I would need some reference describing its implementation.

Thanks for your inputs, Raph