Design Recommendation - COM, ActiveX, DLL

At our company, we need to develop an application that can be updated easily. We have an application that gets connected to our system through a modem (is not a tcp/ip dialup). Our goal is to be able to update the program without having to download the whole executable to the client PC.
The application is not an internet app.
What could be the best way to do this?
Using ActiveX?
Using DLL's? If we use DLL, is it efficient to include the forms on a dll and the events, etc. on another DLL? same DLL? Do I have to worry about this using ActiveX?

I'm kind of lost in this. Accepting any advice, recommendation.

Help is greatly appreciated.

Jose

As regards to your apprehensions about using Active-X dont have any!It is safe to use if the design is proper.
Using an Active X Dll will eliminate the requirement of downloading of the exe on to the clients.Version Control is also an added feature of COM so tommorow if you have some changes in your application just change the DLL and infrom your client to set the reference

As far as the Active X itself is concerned whether is should have all forms in one or different Active X dlls would depend on your applcation and your requirements.I wouldne be able to help you without knowing the details thereof