Killing dll launched from AutoCAD lisp

I have created a DLL that is launched from a lisp routine in AutoCAD (the user clicks a menu item to access the functionality in the dll).

My problem:
Every time a user clicks on the menu item, a new instance of the dll is created (while the previous instance(s) still exist). Each instance of the dll has a connection to a database. Many users and many menu clicks mean lots and lots of pointless database connections.

My question:
How can you kill a dll launched from AutoCAD without closing down AutoCAD? I want to either kill the dll after I'm done with it or kill the previous instance before I create a new instance.

Thank you.....