Blending 3d planes with shader

Hi,

My game spawns several 3d planes (using Instantiate( planePrefabs...) ) and I would need that all my planes alpha-blend (currently I use a texture transparent shader) with everything in my scene (other 3d planes) and not with other similar planes (i.e. instanciated with the same prefab) because they can be spawned one over the other.

This is my shader for transparency:

Shader "Texture only Transparent" {

Properties { _MainTex ("Texture", 2D) = "" }

SubShader { Tags {Queue = Transparent} ZWrite Off Blend SrcAlpha OneMinusSrcAlpha

Pass
{
    SetTexture[_MainTex]
}

} }

I'm very new to shader and I would greatly apreciate some help or any pointers...

Thanks

Mat