[Chimera-users] Removing specific water molecules

Hi, I have a problem using Chimera: I need to delete specific water molecules with a specific residue number, but this number is in common with residues that are useful (such as ligands or co-factors). For example, I type "del :546-893" in the command line in order to delete these water molecules, but I delete also the ligand and FAD and I don't want to. I've read the guide about atom specification, but still I don't know how to do it. Hope someone can help me, thank you. Francesca