Excel VBA Limitations Question

Hi,


I'm writing an application in VB that will consist of two parts.

1) a VERY thin UI layer which just handles events, populating the UI controls etc.

and

2) an ActiveX server (either .dll or .exe) that the UI will call for all it's processing.

I'm using this architecture so the UI can be replaced with one written in another language, and the ActiveX server can be used by another application if necessary.


My question is, what are the limits of VBA in Excel and Word? I need to investigate the possibility of later putting the UI in an Excel application and calling my server from there.


Also (this is very important), can VBA handle asynchronous communication with an ActiveX server using Events and call-back functions. Can it also handle classes.


Thanks for any help you can give me. Please email me if you need more details.


Tom.