The attached sample program contains code to control the Line Output Volume of the N4321.
The program fetches the current volume value of the N4321 at startup and then controls setting the volume up/down with the two buttons. These contain repeated functions to set the volume. Project uses the sliders min and max values (set by double-clicking the slider widget) to control min and max volume allowed on the N4321 Output (Range: 0 - 100 by default).
The slider and accompanying text is for feedback/reference purposes only.