How to make dynamic length dotted arrow / line ?

Hi..

This is basically from editor templates "Physics catapult"

I try to make a dotted line / the aiming arrow..

here is the .c3p dropbox.com/s/bqn6eb4zq0ppxo2/Physics%20catapult%20Arrow.c3p

So far I only think about using Tiledbackground to trick the empty space/alpha channel when repreating images (between each dot)

and I use another helper sprite, because I cannot add image point to tiledbackground for sprite arrow head positioned along aiming (is in touch).. but the arrow head still rotate/move to incorrect position.

Any better way to do this ?