Multipath routing strategies such as Equal-Cost MultiPath (ECMP) are widely used in IP and data-center networks. Most current methods to balance packets over the multiple next hops toward the destination base their decision on a hash computed over selected fields of the packet headers. Because of the non-invertible nature of hash functions, it is hard to determine the values of those fields so as to make the packet follow a specific path in the network. However, several applications might benefit from being able to choose such a path. Therefore, we propose a novel next-hop selection method based on an invertible function. By encoding the selection of successive routers into common fields of packet headers, the proposed method enables end hosts to force their packets to follow a specific path.