Sending a number to a slider, will have the slider report that number. Changing the output of slider with the mouse, also will report a number. Given the output, there's no way (or at least I think) to make a distinction between mousing events and thru events. I've tried to solve this a number of times, when working on user interfaces. It would be great if it were possible to send a message to any ui object to tell it to prepend a certain identifier to it's output whether it is the result of mouse activity. Below patch would then be possible.