rotate a texture inside a cube

i want to rotate a two different texture on the surface of the cube with out rotating the cube cube should remain constant it should not rotate but texture should should rotate continuesly on the cube surface

       var scrollSpeed : float = 0.5;

       function Update() 
       {
       var offset : float = Time.time * scrollSpeed;
       renderer.material.mainTextureOffset = Vector2 (offset, 0);
       }

this is the answer i am looking for