Thank you for your answer, but I don't know the solution. What should I do for a simple GUI, i.e., does sum between three numbers? I would two 3 boxes (a,b,c) for number input and 1 text box (d) for the sum, but the first and the second edit (a and b) have to be the same: so if you set a, b==a, and if you set b, a==b. The number you see in the box have to change too. (d==a+b+c)
Thanks a lot for your answer Best Regards
Pietro Rosi