Do I understand correctly: you are not using the .NET technology or VSTO (the topic of this forum), but classic VB6? If that is the case, we'll need to move the discussion for you to the Word for Developers forum.
We need to understand what kind of comboboxes these are. I'm guessing ActiveX?
I think I understand your problem, but I'm not 100% sure. Could you please provide more information about how you're not able to work with the comboboxes, exactly?