Shader Forge : trying to get refractive particles

Hello everyone,

I discovered Shader Forge a few days ago (which looks to be the best way when you don't code), and now i'm trying to get a heat distortion effect, in order to create a "mirage". I made some tests :

the fact is i always encounter the same problems : the alpha seems to work on the refraction, but the overlapping textures makes me think that particles doesn't calculates each others ; and i get a color + refraction (not obvious on screens) whereas i just want the refraction. I also tried the "stained bump distord" pro package, wich is almost perfect except i don't know how to add an alpha channel

Can someone give me tips to get to a better render ? (I know that i did crappy things with those nodes anyway ^^..)

Thank you, and sorry for my english !