Add/Remove altnet directives to pimd at runtime?

Our network supports many multicast streams using pimd. Many (but not all) of those multicast streams only flow if we use the "altnet multicast_source_ip masklen 24" statement in the phyint section of the pimd.conf file. Those multicast flows are dynamically added or removed as certain network devices are brought up/down based on specific events throughout the day. Throughout the day the pimd.conf file could have these altnet statements added or removed many times. Each time this occurs we have to issue the "pimd -l" command in order for the change to take affect. Each time this command is issued the daemon is reloaded and the mroute table gets wiped. After a short period of rediscovery, the mroutes slowly find their way back into the multicast routing table. This causes a short disruption to pre-existing multicast traffic flow until all of the mroutes are repopulated.

I would like to know if it's possible to add/remove altnet directives without having to edit the pimd.conf file and issue the pimd -l command to reload the config. In other words, could they be added or removed during runtime? Or added without affecting any existing multicast flows/routes?