Multiple transparencies

I have been trying to overlay .png transparencies on a model. For this I apply a base diffuse and add a transparency which I can adjust from full strength down to complete fade. I then wish to add a second transparency over or under this which can also be adjusted, without effecting the other layer(s)
Anyone got any ideas on how to do this?

try this setup:

Thank you, it was not fully what I wanted but it gave me a crucial tip that allowed me to
gain control over two transparencies and a base diffuse texture. Excellent. :slight_smile: