hmm... well I have an idea that might (or might not) work.
I think SPRITEPATH is just redrawing sprites many many times over so that persistence of vision tricks you into thinking that they're moving. If I'm right in my thinking then you should be able to create a timer block that makes the sprite move to different (random) locations.
example:
ON TIMER 5
SELECT CASE 1
 CASE movement_pattern_1
  x = x + 5
  y = y - 5
  TOGGLE movement_pattern_1
 CASE movement_pattern_2
  x = x - 5
  y = y + 5
  TOGGLE movement_pattern_2
 CASE ELSE
  mv = RANDOM 2
  IF mv = 1 THEN movement_pattern_1 = 1
  IF mv = 2 THEN movement_pattern_2 = 1
END SELECT
SPRITE 1 x y $enemy_sprite$
END TIMER
although this would work it would create spastic random convulsions. To effectively use this method (which may or may not work) you'll have to find some way to force the will of an intelligent AI on the select case block as you see fit.
P.S. using smaller SPRITEPATH commands inside the SELECT CASE block might work, but I think your better choice is the first thing mentioned.
P.P.S if this initial block here doesn't work then I spelled something wrong. Sorry