Limit string length of the string control

In some string control using user interface applications need the limited string length option for restrict the user from entering the unnecessary strings .My method for limiting the string length is (See picture 1),

String control connected with String Subset(with length) and the substring connected with the local variable of that string control.String Subset length 10 constant denotes the Maximum string length of that control.Select the update value while typing option of the string control by Right clicking on control for run time string length control. If any other way please let me know.