I have done some intermediate Tk programming, and searched for the same thing sometime ago. I never found any way of changing the contents of that menu. I believe it is not an option, because that would not be within Tk's platform independant functionality (as it is windows specific). But, as always, i am not omnipotent ... maybe someone else has found a way.
$ perl -e 'do() || ! do() ;'
Undefined subroutine &main::try