Theres the easy tween behaviour, or you could lerp it.
put sprites into a family.
if left arrow pressed and variable = stop, set family variable "target_pos" to self.x - what ever, set variable to left.
if variable = left,
distance to "target_pos" > 1, set family.sprites x pos to lerp(self.x, "target_pos", dt*speed)
distance to "target_pos" <= to 1 set variable to stop.