Loading a gui in a new state

I have a question about saving data and then reloading it into an updated gui. I've saved a gui and I'd like to reload it into the newer version of the gui that has more menu options, etc. I realize that what I have below just saves and loads my file in it's current state, but I'd like to be able to keep the data I need and load it into the new gui.

switch gcbo
    case handles.file_menu_load

          [fn working_directory] = uigetfile('*.mat','Select Saved File');
          switch fn
              case 0
                  switch isempty(get(handles.xls_file_box, 'string'))
                      case 1
                          set(handles.xls_file_box,'string','')
                      otherwise
                          set(handles.xls_file_box,'string',...
                              get(handles.xls_file_box, 'string'))
                      end
              otherwise
                  B3D_close('bypass')

                  handles.B3D_fig = hgload(fn);

              end

          case handles.file_menu_save

          N = inputdlg('Enter Name of Save File','FileName');
           hgsave(handles.B3D_fig,[N{1},'.mat'],'all')

end

Thanks!