swap material on a collada object

I have a scene with a collada object and change it’s material default with:

material:MaterialsList=new MaterialsList()
material.addMaterial(Mat01, "name of material 3d Aplication)

I want to change betwen materials in real time with a button
How can I swap a material at runtime?
thanks and sorry for may english

run time behavior is not specified by COLLADA.