Something

set %flag FORWARD


initevents

loop:
 gosub checkFlag
 gosub followFlag
 goto loop

sub checkFlag
 remember:
  set %posX #charposx
  set %posy #charposy
  
  wait 50
  
  if ( #charposx <> %posX ) || ( #charposy <> %posY )
   goto remember
   
  else
  {
   if ( %flag = FORWARD )
    set %flag BACKWARD
   else
    set %flag FORWARD
  }
return
 
sub followFlag
 if ( %flag = FORWARD )
  msg Slow Forward $
 if ( %flag = BACKWARD )
  msg Back $
 wait 50
return