[LIBGDX] skinning a cube with multiple textures

Newbie & Debugging Questions
#1

Hi everyone,

i have created a ModelInstance in libgdx with


cube = new ModelBuilder().createBox(block_size, block_size/2, block_size,
		        new Material(), Usage.Position | Usage.Normal | Usage.TextureCoordinates);

instance = new ModelInstance(cube, 0, 0, 0);

and now i want to skin the 6 sides of this cube with different textures.
when i set a texture with


instance.materials.get(0).set(TextureAttribute.createDiffuse(texture));

all six sides have this texture streched to the size of each rectangle.
this lets me suppose, there is a way, to set a texture for each side

http://s1.postimg.org/5br36hywf/screen.png

http://s27.postimg.org/fswbjw44v/grasssmile.png

i have searched the net for a few hours now and nowhere i can find something with multiple textures

my regards!