>... < snip > ... To let the user see the value change immediately, when he clicks on the checkbox, I must put in the interactivechange of the checkbox the code 'this.refresh'. If you have many checkbox, as I have....

Is THIS.REFRESH the only line of code in the InteractiveChange or Click methods? Do you have any code in those methods of your checkbox in any of your checkbox classes that this control is subclassed from? If so, you will need a DoDefault() command.