Trouble With Shader

Hey, I've been trying to reproduce the effects of an OpenGL shader but I don't know much about neither OpenGL or Shaders. So far I've found that the Additive shader in Unity recreates most of what I want, however it seems like I need the alpha channel to taken into consideration as well.

My reference code uses

gl.blendFunc( D3DBLEND_SRCALPHA, D3DBLEND_DESTALPHA );

I then searched for the source code of the Mobile/Particles/Additive and found this

Code (CSharp):

1. Shader "Effects/Custom" {
2.     Properties{
3.         _MainTex("Particle Texture", 2D) = "white" {}
4.     }
5.  
6.     Category{
7.         Tags { "Queue" = "Transparent" "IgnoreProjector" = "True" "RenderType" = "Transparent" }
8.         Blend SrcAlpha One
9.         Cull Off Lighting Off ZWrite Off Fog { Color(0,0,0,0) }
10.  
11.         BindChannels {
12.             Bind "Color", color
13.             Bind "Vertex", vertex
14.             Bind "TexCoord", texcoord
15.         }
16.  
17.         SubShader {
18.             Pass {
19.                 SetTexture[_MainTex] {
20.                     combine texture * primary
21.                 }
22.             }
23.         }
24.     }
25. }

But I can't seem to get it working with

Blend SrcAlpha DstAlpha

This is the result with the shader untouched


And this is what my reference looks like



Can anyone help me sort this out?