If you don't know the name of the function at runtime that you need then the dll is pretty much useless to you. Though there is a way to find out all the functions in a dll (load it up in a hex editor and look towards the end of the dll).

If you want a plug-in type archetecture like netscape or ie, you need to design an interface (a blank class with all the functions you will need a dll to support compiled into a dll) that any new dll will use (implements <interface name>). This way, if you need the dll to run code that modifies something, you pass the data to a known function that is available to any dll you load.

To load a dll that you don't know about until runtime, keep an ini file, a registry setting, or some other way to store the dll names in and do something along these lines:
Code:
Dim myDLL As Object

Set myDLL = CreateObject(myDLLName & "." & myDLLObject)
I'm fully unsure if this will work, but you can give it a try