How to change detail albedo x2 texture from script

Hello, have a face of my character that is a part of my model. It has a base texture and on top of it - albedo x2 texture to set its facial expression. What I am trying to do is to change the second texture when something happens (let's say player gets in range or character gets hit). So the problem is that from scripts, I can only find how to change main texture. Any tips how to change texture for detail? Thank you in advance

 

The only way out atm I see making a material with x2 textures.. But I don't really like the idea..