FVWM window changing

The FVWM wiki has the magic incantation to make Alt-Tab do what you want. Since I'm using X11 in a single window in Windows, I replace the final line with "Key Tab A CM SwitchWindow" to change windows within X11.

   SetEnv DIR Next


   AddToFunc FocusRaiseAndStuff
   + I Iconify off
   + I Focus
   + I Raise

   AddToFunc SwitchWindow
   + I $[DIR] (CurrentPage, !Iconic, !Sticky) FocusRaiseAndStuff
   + I Deschedule 134000
   + I PipeRead `[ "$[DIR]" == "Prev" ] && \
       echo 'SetEnv NDIR Next' || \
       echo 'SetEnv NDIR Prev'`
   + I Schedule 700 134000 SetEnv DIR $[NDIR]

   Key Tab A M  SwitchWindow