Validation of dependent properties in a "live edit" WPF app

Question

I'm working on an app which supports live editing. That is you update properties in one area and their impact is seen in another with hitting "apply". Happens to be a charting app. One such edit "group" allows specifying a range. A triple range in fact: High, Target and Low.

Our validation is such that High must be greater than target, target must be greater than Low (rocket science).

Our dilemma is that the visual experience is a bit jarring when someone wants to go from say 30,20,10 to 15,10,5. I'm curious if anyone has implemented a mechanism for this scenario that might fit well in our situation such that we don't "yell" at the user as they change the range values.

Answer 1

The key is to alert users that something is wrong without interrupting them.

Perhaps something like this:

If this is still too loud, you can get rid of the red fill and just use red outlines.