Choice:InsBlock: public: code_block
  This code block is activated from Choice:Process() when the Choice:Append
  is true and the user pressed Ins key during the selection. As parameter
  of this code block is passed the self object. The job of this code block
  is to add a new item to Choice:Items, or to reconfigure the instvar
  variables of this object. It enables during the selection
  the adition/deletion of menu items and dynamicaly modify the menu.