I think I see what you want to do, but you are either being hopelessly optimistic, are very fortune in super-simple originals, or have a lot of work ahead of you.
I suspect you should be looking for TIFF -> OCR -> Excel products. Involving PDF before the end is going to make a world of pain.
The crucial problem in going from a printed page, TIFF, to Excel is that no software knows where the rows and columns really are.