Projecting an appended Texture.

I'm using projector to project an "arrow" to the surface, with various projector size. However , in order to preserve the size and prevent stretching i want to use 3 textures (with repeating of the body).

I know i can use 3 projectors and have each of them project separate part/texture of the arrow, but i was wondering if there's perhaps a simpler solution to this.

Maybe a shader that can append these textures, so i can use only one projector (and one shader effectively)?

Maybe i can programatically "create" the desired combined texture and apply it to the single shader?

Perhaps there is a shader i can modify to create the desired behaviour or some code snippet to make the texture-merge programatically and apply it to the shader or maybe some different approach ?

I use this for indicating aim/range in an isometric game (Diablo /Torchlight/LoL). (Posted this in the forums also)