Selecting DLL's at runtime

Hi,

Here's what I'm faced with.

A DLL provided by a card manufacturer, now has 3 versions in service.
I have all 3 versions, the dates as well as the sizes are different, however the names are the same.

The DLL has to be registered to run, so I believe I can get version-related info from the registry if necessary.
As the manufacturer has improved their product over the years, we’ve had to accommodate the changes. Now we find we are having to update our software on older systems, and some of them have the older hardware and require the earlier version DLL’s.

So, how do I go about this?
I have changed the names of each DLL, and ideally, I would like to register all 3 and then let the program determine which one should be used.
Only 1 DLL will be used and will likely be the only one ever used on that system(barring a card failure, etc.). Since the routine names are the same, how do I reference the appropriate DLL using a single set of routines rather than 3 different sets?

I have considered letting the Setup Program make the determination, but in order to get card parameters, the right DLL has to be loaded. So that starts to get ugly.
Also we can’t allow the user to make the decision about which one to use.

Thanks all!