fields as multiple switches

Given: an array with (more than) 3 columns. One is an on/off switch. Another is a unique identifier. The third is a list of other unique identifiers "linked" to that row/entry. When a given entry is turned "on",all the items in it's list are also turned on, and vice versa. I'm attaching a simple example, though in the real world the identifiers are code numbers, so they are things like 603.4 and 709.4.2.1.3

Any thoughts on an easyish way to do this? I think of using a macro associated with cell/worksheet changes, but then parsing the list and searching seems likely to be slow. Thanks for any help.

Keith