You can add code at run time as well. You need to set a reference to Visual Basic Extensibility, but, I saw, I think Damon Ostrander, make a suggestion, like this:
If you know you MAY add a checkbox at run time, and you need the_Click() sub, you can create the Sub at Design time with the name of the control you will have at run time, that way, if the control is added, it'll have its _Click() event.