which languages to use?

Hi all,

for study purposes I need to write a Word-AddIn, so I wondered in what
languages I need to acquire knowledge. The AddIn is supposed to
fulfill the following requirements:

I need a bar with symbols with a click on a symbol, a dialog box
(designed by me) pops up. In there the user can enter information
about a JavaApplet, a FlashMovie, or other "objects". When confirming
the dialog box, a placeholder for this object is placed in the
word-document, which holds the information entered in the dialog box
(preferrably a symbol, text is also possible) - I planned to do that
with the word component "field".

The goad is that the "objects" only take little space in the document
and refere to the applet, movie, etc., but to have the posibillity to
safe the document as a XML-file (Word 2003) and transform it via xslt
into a web-page, where the "objects" are replaced by the real applet,
movie, etc.

So far I've heard that this kind of AddIn has to be written as a
COM-dll, and that it is possible to write these AddIns in c++ or vb.
Which language is (for my purpose) better? (So far, I found more
literature on writing dll's in c++)

My language skills in VB and C++ are limited on what is written in a
standard beginners book: basic data types, control flow, methods,
classes, inheritance,... From there on, there are (in my oppinion)
many directions to go, so which langauges / skills would you
recommand? Any literature suggestions?

Another point: Is it possible to call a method that opens my dialog
box when the user double-clicks on the placeholder inserted in the
word document, so the user can not only insert placeholders in the
document, but modify them?

Thanks a lot for any recommendation,
Langi
.