simple shader that cross between two texture2d objects

Forgive me for my ignorance, i’ve never paid much attention to shaders until now
I’m looking for a simple shader to do something slide this

Texture2d visibleTexture = myShader.crossFade(texture_1, texture2,.4f);
GUI.DrawTexture( rect, visibleTexture);

http://www.unifycommunity.com/wiki/index.php?title=Blend_2_Textures

thanks!