How to fill image relative to touch

So basically what I'm trying to do is to touch a certain object, this object will instantiate 4 arrows, and then fill one of the arrows by touch, so if I'm moving my finger right, it will fill the right arrow following my touch point etc. I've tried several ways using UI elements, but it doesn't feel like it's perfectly suited for this function...

Please HELP!

Thanks in advance, Omer