Hi,

the simplest is if you can export your columns of datas into CSV
format. Then you can just read it with the 'csv' libary. See
http://ruby-doc.org/stdlib/libdoc/csv/rdoc/index.html for some usage.
Then it's just a matter of opening the CSV, get the values you want
out of it, and feed them to Gruff.

I'm sure it's also possible to connect to the Access database using
ADO under windows, but it's going to be a bit harder I think. If it's
only a tool for you, I would keep the CSV version, otherwise invest
some time in the ADO version once the first-one is working.