I've just found your post following a Google search as I have been wondering whether I can add shipping costs by uploading a csv file from the many shipping spreadsheets I have created. I have designed a silicone keyboard with sunken keys for people with cerebral palsy like myself, Parkinson's, etc or who have a visual impairment.
It is taking me an age to enter shipping costs and I find myself wishing that I could download what I have already entered, as a csv file, paste my prices in, and upload it. Wouldn't that be so simple!
If you could e-mail me your program, I would be extremely grateful.
website (at) lime-at (dot) com
I wrote a program which handled this for me. If you are in need of this please feel free to message me.