How to rewrite Vray material?

Hello, how do you rewrite Vray material in Vray 3? I need to rewrite existing materials with new ones, which i have as vismat files. I don´t want to create new materials, because i would need to reassign them. I cannot use the function “use as replacement” and “replace” because in doesnt replace those materials which are assigned to layer. Ideally, I just want to change the material definition as i was able in Vray 2- rignt click on material and choose vismat file. Is it possible? Thanks