How do I modify a very basic blend shader to allow both transparent textures?

I am making an iOS game and need to blend two textures with alpha back and forth.

I don’t need lots of control, there are no lights or anything affecting this shader. I found a very basic blend shader that I’ve seen referenced several times, but I don’t know how to enable transparency for both _MainTex and _Texture2.

This shader does everything I need except allow textures with transparency.

Shader "Custom/Blend 2 Textures" { 

Properties {
	_Blend ("Blend", Range (0, 1) ) = 0.5 
	_MainTex ("Texture 1", 2D) = "" 
	_Texture2 ("Texture 2", 2D) = ""
}

SubShader {	
	Pass {
		SetTexture[_MainTex]
		SetTexture[_Texture2] { 
			ConstantColor (0,0,0, [_Blend]) 
			Combine texture Lerp(constant) previous
		}		
	}
} 

}

Here’s all that the texture needs to do:
1)Texture A is visible
2)Texture B is visible.
3) For .3 seconds they blend from A to B and at other times blend for 0.3 seconds B to A.

As you can see in the image below, there are numbers in focus and out of focus. Rather than a blurring shader to fake depth of field (since I’m using Unity Basic), I just want to fade back and forth between blurred and unblurred textures.

I get the feeling that as soon as I add transparency there’s a lot more I have to do. Any help is very much appreciated. I’m new to custom shaders, so not sure if I bit off too much. So can I easily make both textures A and B contain transparency?

alt text

I’ve not spent much time with shader to date, but this should give you what you want:

Shader "Custom/Blend 2 Textures" { 
 
Properties {
    _Blend ("Blend", Range (0, 1) ) = 0.5 
    _MainTex ("Texture 1", 2D) = "" 
    _Texture2 ("Texture 2", 2D) = ""
}
 
SubShader { 
	Tags {"Queue"="Transparent"}
	Blend SrcAlpha OneMinusSrcAlpha
    Pass {
       SetTexture[_MainTex]
       SetTexture[_Texture2] { 
         ConstantColor (0,0,0, [_Blend]) 
         Combine texture Lerp(constant) previous
       }     
    }
} 

}