I don't understand why its usual to assume that the only two choices are * show N/A everywhere * silently ignore sources of potential errors. Why not make

I don't understand why its usual to assume that the only two choices are * show N/A everywhere * silently ignore sources of potential errors. Why not make the calculation while adding a visual cue (e.g. a yellow or red indicator in the corner) that marks the field as tainted? Now the users get to decide whether they want to investigate or ignore that.