I am not highly knowledgeable about com+ so someone else will need to help you with that.

About the DLL suggestion. You might set a flag in an INI or Registry entry that would tell all the apps to unload the dll. Thats a simplistic approach. Each application could check the flag every x amount of seconds. You set the flag, retry removing the DLL every x seconds until you can, then set the flag back to tell all the apps to reload it.

This is just one method and may not be the best for your solution. It just provides a way of looking at it.