[Chimera-users] command @/serialNumber=#

Hello: I wonder whether it is possible to extend the command sel @/serialNumber=18801 (as an example of a particular serial number) to comprise a range of atoms. So as to cover, for example, an entire ligand, may be dioxygen, 18801-18802. And whether that could be extended to define a centroid. it is implied that I have prepared a large system based on segname (charmm ff with namd), which is not dealt with by chimera. thanks francesco pietra PS: I can follow the ligand by defining the centroid for a single atom of the ligand. This would be my last resource.