Skinned models / Vertex Data

hi, i am facing a little problem concerning vertex data. i would like to use engine created object oriented bounding boxes for macro collision checks. i implemented this using the jacobi method, retrieving the eigenvectors and the centroid to build the bounding box. it works fine with static meshes. the problem arises when i try to port this algorythm to skinned models. a quick point draw of the vertices retrieved by this method:

        protected override Vector3[] GetVertices()
            // To do this, the mesh must exist
            if (mesh != null)
            {
                // This will get the verts info from the vertex buffer
                GraphicsStream stm = mesh.VertexBuffer.Lock(0, 0, LockFlags.None);

                // The vertices to be returned
                Vector3[] v = new Vector3[mesh.NumberVertices];

                // Loop through the vertices
                for (int i = 0; i < mesh.NumberVertices; i++)
                {
                    // Get the current vertex info
                    v = (Vector3)stm.Read(typeof(Vector3));
                }
                // Unlock the vertex buffer
                mesh.VertexBuffer.Unlock();

                // Return the vertices
                return v;
            }
            return null;
        }

shows that the vertices do not move, and are (probably) stuck in the model's original position (ie, not affected by skeleton influences). so what i would like to ask is, how do i access properly the vertex data to get the skeleton weighted vertices positions?