When editing a formula, the cell involved should be highlighted with different colours

When editing a formula, the cell involved should be highlighted with different colours

 Hi everybody,
IMHO when I edit a cell containing a formula, it would be very useful (and usable ) to have the cell involved highlighted with different colors. Example =C3+C1. C3 should be green as well as the C3 cell borders. Same thing for C1...what do you think??