John. Glad it helped a little at least.

Have you looked around Dosadi's site? They also have a package (under Products) called CTwain, which is a library with source for use in building TWAIN apps. Their licencing is very generous in that it "may be freely used for non-commercial purposes". It is designed for exactly your purpose I think.

They also have a support dept. which, going by my one intereaction with them, seems very knowledgable, efficient and flexible. A rarity these days.

I'd suggest you contact them, tell them what you are trying to do, and maybe they will be able to give you some pointers. Good luck