Your best bet would be to ask on the Visual Novel Maker forum and see if calling on dll files is even possible. If not, Macrotune would have to be completely rewritten in Javascript and I don't have time for that. Sorry I couldn't be more help.
It should be possible. Would you be able to if I could figure out how? (I was told that it could be done, but I need to read the documentation to figure out how it works)
And if not, I'm in no major rush if you'd be willing to do make a javascript version later on.
Anyways, let me know how much it would cost to have a 64 bit version made.