Circular Textured Healthbar with transparent background

Before I state my question, I wan tot say that I already tried Eric5h5’s solution using aplha cutoff and that does not give me the result I’m looking for.

Here is a screenshot of the texture I’m trying to turn into a healthbar:

I want to be able to mask out(somehow) parts of the texture based on a value. I’ve tried Eric5h5’s solution which allows me to get a nice circular cutout but it doesn’t allow me to have it textured, it would be nice to be able to apply the alpha culling of his solution to support using a textured base. I’ve tried a few shaders for masking textures but those don’t allow me to control the mask the way I need to. Also I can’t use a segmented healthbar, those don’t look very good, I’d also like to avoid NGUI. Any solution is welcome no matter how complicated as long as it is properly documented and not inefficient.

How about a really simple AlphaTest shader:

Shader "Custom/AlphaTest" {
	Properties {
		_MainTex ("Base (RGB) Transparency (A)", 2D) = "" {}
		_Blend ("Blend", Range (0, 1) ) = 0.5

	}
	SubShader {
		Pass {
			AlphaTest LEQUAL [_Blend]
			SetTexture [_MainTex] { combine texture }
		}
	}
}