change materialCollection node parameter via BP

im creating a city with lots of material and texture for the buildings and i want to create a day and night system where at night the light on the texture is turn on.
basicly i have an emission map that i want to multiply by the material collection value so i can control all the light at once.
but i have hundreds of building and i want to automate the creation of the material collection on the material of every building. its all find including creating the material collection node and connecting it via blueprint. what i need to know is how can i change the parameters of the newly created material collection?
how can i point it to a certain collection and parameters name (the red circle on the picture) via blueprint?
thanks in advance