In order to get the LST to move, you need a loop the sets its position on the X axis.
move = false
#loop
_x = getpos <LST name> select 0
_y = getpos <LST name> select 1
<LST name> setpos [(_x - <distance to move per millisecond>),_y,0]
~.001
?not(move) : goto "loop"
this situation is perfect for cutscenes