Ok, this post is 2 mos. old now... So I'm guessing that you've very likely gotten this sorted by now....
But I would guess that you would not need the Professional Version. This is just based on my experience with VB.Net Standard vs. VB.Net Professional. Basically they are the same, it's just that the "Standard" version lacks things like a "Class Library" project and the like.
Now you wish to make a DLL that can be called by VB.Net, so not having a "Class Library" would be annoying... but not that big of a deal. You can get around it in VB.Net easily by simply editing the .vbproj file and changing OutputType = "WinExe" to be OutputType = "Library". That's it.
I would think that the adjustments for a C++ project would be similar? You might also try kicking around the
Visual C++ 2005 Express Beta. Being 2.0, of course, it would have added features, but you could kick it around for free and it is "conceptually" the same as the stand-alone "Standard" versions.
Anyway, something tells me you must have gotten this solved long, long ago... Hope this is of some help anyway...
,
Mike