Override to force recomputing the list. This is tricky because LoadMatches calls a Clerk routine which recursively calls ReloadList. Therefore if we call LoadMatches, we don't need to call the base routine. If we're in the middle of loading a list, though, we want to only do the base thing. Finally, if the OwningControl has never been loaded (user hasn't yet selected option), just load the (typically empty) list.