uicontrol does not have ValueChangingFcn. That callback is only for App Designer "web figures" and never for "traditional figures", but uicontrol exists only for traditional figures.
The App Designer analog of uicontrol sliders is uislider()
If you need to know when a user has stopped moving a uicontrol slider then code the Callback property to start a timer object with the appropriate timeout. If Callback gets called again before the timer expires then restart the timer. Either way, timer was active or not, proceed with the work you would have liked to have done with a ValueChangingFcn callback if those existed. In other words uicontrol slider's equivalent to ValueChangingFcn is Callback property.
When the timer callback gets called, do the work that you would have liked to do in a ValueChangedFcn callback. uicontrol slider has no property equivalent to ValueChangedFcn callback, so this timer work is how you can do the equivalent.
If you want ValueChangingFcn but not ValueChangedFcn then do not bother with the timer, just use Callback property.
