if u woldv use bullet behavior u wold had the distance traveled.. however since your object is not a bullet and u dont want to mix the 2 of them cause of obvious glitches..
create a instance variable on the player with the movement controls.
when any key is pressed (left or right) that enables the movement, triger one time set the instance variable (lets say posx) to players.x then
compare two variables : distance(player.x,0,player.posx,0) is less then 250 simulate left or right control. that way ur char will only move when the buttons are pressed if the distance is less then 250 pixels. then when u release and press again everything should restart itself.
Distance limited movement
if that is what ur not looking for, then what plinkie said for the "teleporting movement"setting the .x to + 250 or -250 wold do it.