The really critical thing to me is the scrupulous, painstaking effort required of mere human beings to keep spreadsheets that are consistent internally, let alone from one to the next, over time. Still, if they really did keep text out of the number columns, comments out of the date columns, etc., then great! VisualBasic talks to Excel and the rest is a walkover.
I once did a tiny little contract job for a University here which converted 300+ spreadsheets to Access(these were Lotus, now that I think of it). I used plain vanilla VisualBasic, as I recall. The tricky part was recognizing the header row or skipping it, but it wasn't that bad. I think I saved the code, but it wasn't very user-friendly, since I was the only user, and once it ran, I only ran it once. A lot of stuff was hard-coded that should really have been event-driven, etc.
Ron