iTween - look for new path, move to or reverse at end?

I would like my object to look for a new path when it reaches the end of current path. if new path is found (within x distance) object moves to and follows new path. if no path is found object reverses direction on current path. I am very new to unity, my background is modeling and animating in 3ds, very new to coding, sorry (hopefully) if there is simple answer, but could not find it searching, thanks