onMotion

                case "Hypixel":
                    if (event.isPre()) {
                        final int curSlot = mc.thePlayer.inventory.currentItem;
                        final int spoof = curSlot == 0 ? 1 : -1;
                            mc.getNetHandler().addToSendQueue(new C09PacketHeldItemChange(curSlot + spoof));

                        mc.getNetHandler().addToSendQueue(new C09PacketHeldItemChange(curSlot));
                    }

                    if (event.isPost()) {
                        mc.getNetHandler().addToSendQueue(new C08PacketPlayerBlockPlacement(mc.thePlayer.inventory.getCurrentItem()));
                    }
                    break;

on Packet

            case "Hypixel":
                if (event.getPacket() instanceof S30PacketWindowItems)
                    if(mc.thePlayer.isUsingItem()) {
                        event.cancelEvent();
                    }
                break;