ok,i know

        private void BtnPosToZero_Click(object sender, EventArgs e)
        {
            IInterface iface = global.COREInterface;
            IInterval interval = global.Interval.Create();

            for (int i = 0; i < iface.SelNodeCount; ++i)
            {
                IINode node = iface.GetSelNode(i);


                interval.SetInfinite();
                IMatrix3 nodeTM = node.GetObjectTM(0, interval);
                node.SetNodeTM(0, nodeTM);

                IMatrix3 ZeroMatrix3 = global.Matrix3.Create();
                ZeroMatrix3.SetScale(global.Point3.Create(new float[3] { 1, 1, 1 }));
                node.SetNodeTM(0,ZeroMatrix3);
            }
            iface.ForceCompleteRedraw(false);
        }